diff --git a/ReleaseNotes b/ReleaseNotes
index fa18ff7246..dc0d3df1e2 100644
--- a/ReleaseNotes
+++ b/ReleaseNotes
@@ -2547,7 +2547,7 @@ Bugfixes include:
     * FAT.  Now returns the correct error value when it is unable to
       recognize the file system.
 
-    * Build.  MAC OS build fixes (submitted by Mike Smith)
+    * Build.  macOS build fixes (submitted by Mike Smith)
 
 And several others.  See the ChangeLog for more details.
 
@@ -26659,11 +26659,11 @@ This is the first release of NuttX as Apache NuttX (Incubating) and represents o
            - NXP S32K11x (Cortex-M0+) and S32K14x (Cortext-M4F): Add support for NXP automotive boards.
            - XMC 4700 (Cortex-M4F)
        * Architectures with significant improvements
-           - ESP32 loadable modules support 
-           - i.MX RT: FLEXIO clock config logic. 
+           - ESP32 loadable modules support
+           - i.MX RT: FLEXIO clock config logic.
            - Fix the clock configuration for the i.MX RT family
-           - i.MX RT: Add ability to run from OCRAM 
-           - SAMA5D27 peripheral support - USB Host working 
+           - i.MX RT: Add ability to run from OCRAM
+           - SAMA5D27 peripheral support - USB Host working
            - z20x: Add W25 bootloader
            - i.MX RT: Add USB Device support
            - STM32, STM32F7, STM32H7 add SPI DMATHRESHOLD
diff --git a/arch/arm/src/arm/Toolchain.defs b/arch/arm/src/arm/Toolchain.defs
index 1f377ed7b4..ca36ccb386 100644
--- a/arch/arm/src/arm/Toolchain.defs
+++ b/arch/arm/src/arm/Toolchain.defs
@@ -142,7 +142,7 @@ ifeq ($(CONFIG_ARM_TOOLCHAIN),DEVKITARM)
   endif
 endif
 
-# Generic GNU EABI toolchain on OS X, Linux or any typical Posix system
+# Generic GNU EABI toolchain on macOS, Linux or any typical Posix system
 
 ifeq ($(CONFIG_ARM_TOOLCHAIN),GNU_EABIL)
   CROSSDEV ?= arm-none-eabi-
diff --git a/arch/arm/src/armv6-m/Toolchain.defs b/arch/arm/src/armv6-m/Toolchain.defs
index 3ebaf1aa6c..91d3974e65 100644
--- a/arch/arm/src/armv6-m/Toolchain.defs
+++ b/arch/arm/src/armv6-m/Toolchain.defs
@@ -168,7 +168,7 @@ ifeq ($(CONFIG_ARMV6M_TOOLCHAIN),DEVKITARM)
   ARCHCPUFLAGS = -mcpu=cortex-m0 -mthumb -mfloat-abi=soft
 endif
 
-# Generic GNU EABI toolchain on OS X, Linux or any typical Posix system
+# Generic GNU EABI toolchain on macOS, Linux or any typical Posix system
 
 ifeq ($(CONFIG_ARMV6M_TOOLCHAIN),GNU_EABIL)
   CROSSDEV ?= arm-none-eabi-
diff --git a/arch/arm/src/armv7-a/Toolchain.defs b/arch/arm/src/armv7-a/Toolchain.defs
index 971558cb74..18b0d4de43 100644
--- a/arch/arm/src/armv7-a/Toolchain.defs
+++ b/arch/arm/src/armv7-a/Toolchain.defs
@@ -160,7 +160,7 @@ ifeq ($(CONFIG_ARMV7A_TOOLCHAIN),DEVKITARM)
   endif
 endif
 
-# Generic GNU EABI toolchain on OS X, Linux or any typical Posix system
+# Generic GNU EABI toolchain on macOS, Linux or any typical Posix system
 
 ifeq ($(CONFIG_ARMV7A_TOOLCHAIN),GNU_EABIL)
   CROSSDEV ?= $(TARGET_ARCH)-none-eabi-
diff --git a/arch/arm/src/armv7-m/Toolchain.defs b/arch/arm/src/armv7-m/Toolchain.defs
index 71bd13e593..2f425db6f6 100644
--- a/arch/arm/src/armv7-m/Toolchain.defs
+++ b/arch/arm/src/armv7-m/Toolchain.defs
@@ -231,7 +231,7 @@ ifeq ($(CONFIG_ARMV7M_TOOLCHAIN),DEVKITARM)
   ARCHCPUFLAGS = $(TOOLCHAIN_MCPU) -mthumb $(TOOLCHAIN_MFLOAT)
 endif
 
-# Generic GNU EABI toolchain on OS X, Linux or any typical Posix system
+# Generic GNU EABI toolchain on macOS, Linux or any typical Posix system
 
 ifeq ($(CONFIG_ARMV7M_TOOLCHAIN),GNU_EABIL)
   CROSSDEV ?= arm-none-eabi-
@@ -252,7 +252,7 @@ ifeq ($(CONFIG_ARMV7M_TOOLCHAIN),GNU_EABIW)
   endif
 endif
 
-# Clang toolchain on OS X, Linux or any typical Posix system
+# Clang toolchain on macOS, Linux or any typical Posix system
 
 ifeq ($(CONFIG_ARMV7M_TOOLCHAIN),CLANGL)
   CROSSDEV ?= arm-none-eabi-
diff --git a/arch/arm/src/armv7-r/Toolchain.defs b/arch/arm/src/armv7-r/Toolchain.defs
index f1eb9db817..c545152afb 100644
--- a/arch/arm/src/armv7-r/Toolchain.defs
+++ b/arch/arm/src/armv7-r/Toolchain.defs
@@ -142,7 +142,7 @@ ifeq ($(CONFIG_ARMV7R_TOOLCHAIN),DEVKITARM)
   endif
 endif
 
-# Generic GNU EABI toolchain on OS X, Linux or any typical Posix system
+# Generic GNU EABI toolchain on macOS, Linux or any typical Posix system
 
 ifeq ($(CONFIG_ARMV7R_TOOLCHAIN),GNU_EABIL)
   CROSSDEV ?= $(TARGET_ARCH)-none-eabi-
diff --git a/arch/avr/src/avr/Kconfig b/arch/avr/src/avr/Kconfig
index d313faf43a..e044b77a91 100644
--- a/arch/avr/src/avr/Kconfig
+++ b/arch/avr/src/avr/Kconfig
@@ -43,7 +43,7 @@ config AVR_CROSSPACK_TOOLCHAIN
 	bool "CrossPack-AVR"
 	depends on HOST_MACOS
 	---help---
-		For OS X, the AVR CrossPack toolchain is supported:
+		For macOS, the AVR CrossPack toolchain is supported:
 		http://www.obdev.at/products/crosspack/index.html
 
 config AVR_BUILDROOT_TOOLCHAIN
diff --git a/arch/avr/src/avr/Toolchain.defs b/arch/avr/src/avr/Toolchain.defs
index 7503086fb0..65fabd24a6 100644
--- a/arch/avr/src/avr/Toolchain.defs
+++ b/arch/avr/src/avr/Toolchain.defs
@@ -104,7 +104,7 @@ ifeq ($(CONFIG_AVR_TOOLCHAIN),BUILDROOT)
   LDFLAGS += -nostartfiles -nodefaultlibs
 endif
 
-# AVR CrossPack under OS X
+# AVR CrossPack under macOS
 
 ifeq ($(CONFIG_AVR_TOOLCHAIN),CROSSPACK)
   CROSSDEV ?= avr-
diff --git a/arch/mips/src/mips32/Kconfig b/arch/mips/src/mips32/Kconfig
index 75beadf504..f3f1b73430 100644
--- a/arch/mips/src/mips32/Kconfig
+++ b/arch/mips/src/mips32/Kconfig
@@ -59,7 +59,7 @@ config MIPS32_TOOLCHAIN_PINGUINOW
 	select ARCH_TOOLCHAIN_GNU
 
 config MIPS32_TOOLCHAIN_PINGUINOL
-	bool "Pinguino mips-elf toolchain under OS X or Linux"
+	bool "Pinguino mips-elf toolchain under macOS or Linux"
 	depends on HOST_LINUX || HOST_MACOS
 	select ARCH_TOOLCHAIN_GNU
 
diff --git a/arch/mips/src/mips32/Toolchain.defs b/arch/mips/src/mips32/Toolchain.defs
index 909116df90..c76b0d800b 100644
--- a/arch/mips/src/mips32/Toolchain.defs
+++ b/arch/mips/src/mips32/Toolchain.defs
@@ -144,7 +144,7 @@ else
   MIPS_MICROMIPS =
 endif
 
-# Generic GNU mip32 toolchain on OS X or Linux
+# Generic GNU mip32 toolchain on macOS or Linux
 
 ifeq ($(CONFIG_MIPS32_TOOLCHAIN),GNU_ELF)
   CROSSDEV ?= mips-elf-
diff --git a/arch/misoc/src/lm32/Toolchain.defs b/arch/misoc/src/lm32/Toolchain.defs
index f59fa1ab45..0796cf079a 100644
--- a/arch/misoc/src/lm32/Toolchain.defs
+++ b/arch/misoc/src/lm32/Toolchain.defs
@@ -84,7 +84,7 @@ ifeq ($(CONFIG_LM32_TOOLCHAIN),BUILDROOT)
   MAXOPTIMIZATION ?= -Os
 endif
 
-# Generic GNU toolchain on OS X, Linux or any typical Posix system
+# Generic GNU toolchain on macOS, Linux or any typical Posix system
 
 ifeq ($(CONFIG_LM32_TOOLCHAIN),GNUL)
   CROSSDEV ?= lm32-elf-
diff --git a/arch/or1k/src/mor1kx/Toolchain.defs b/arch/or1k/src/mor1kx/Toolchain.defs
index 1a3d38f5b6..720cb304e6 100644
--- a/arch/or1k/src/mor1kx/Toolchain.defs
+++ b/arch/or1k/src/mor1kx/Toolchain.defs
@@ -59,7 +59,7 @@ ifeq ($(CONFIG_ARCH_OR1K_MOR1KX),y)
 else
 endif
 
-# Generic GNU or1k toolchain on OS X or Linux
+# Generic GNU or1k toolchain on macOS or Linux
 
 #ifeq ($(CONFIG_OR1K_TOOLCHAIN),GNU_ELF)
 CROSSDEV ?= or1k-elf-
diff --git a/arch/risc-v/src/rv32im/Toolchain.defs b/arch/risc-v/src/rv32im/Toolchain.defs
index 612959aaee..669edb7d72 100644
--- a/arch/risc-v/src/rv32im/Toolchain.defs
+++ b/arch/risc-v/src/rv32im/Toolchain.defs
@@ -74,7 +74,7 @@ ifeq ($(CONFIG_DEBUG_CUSTOMOPT),y)
   MAXOPTIMIZATION := $(CONFIG_DEBUG_OPTLEVEL)
 endif
 
-# Generic GNU RVG toolchain on OS X, Linux or any typical Posix system
+# Generic GNU RVG toolchain on macOS, Linux or any typical Posix system
 
 ifeq ($(CONFIG_RISCV_TOOLCHAIN),GNU_RVGL)
   CROSSDEV ?= riscv64-unknown-elf-
diff --git a/arch/risc-v/src/rv64gc/Toolchain.defs b/arch/risc-v/src/rv64gc/Toolchain.defs
index dbca46b1a9..91698dc568 100644
--- a/arch/risc-v/src/rv64gc/Toolchain.defs
+++ b/arch/risc-v/src/rv64gc/Toolchain.defs
@@ -70,7 +70,7 @@ ifeq ($(CONFIG_DEBUG_CUSTOMOPT),y)
   MAXOPTIMIZATION := $(CONFIG_DEBUG_OPTLEVEL)
 endif
 
-# Generic GNU RVG toolchain on OS X, Linux or any typical Posix system
+# Generic GNU RVG toolchain on macOS, Linux or any typical Posix system
 
 ifeq ($(CONFIG_RISCV_TOOLCHAIN),GNU_RVGL)
   CROSSDEV ?= riscv64-unknown-elf-
diff --git a/arch/sim/Kconfig b/arch/sim/Kconfig
index aa4d0a6020..6e8a72e492 100644
--- a/arch/sim/Kconfig
+++ b/arch/sim/Kconfig
@@ -67,7 +67,7 @@ config SIM_X8664_SYSTEMV
 	bool "System V AMD64 ABI"
 	---help---
 		The calling convention of the System V AMD64 ABI is followed on Solaris,
-		Linux, FreeBSD, Mac OS X, and other UNIX-like or POSIX-compliant operating
+		Linux, FreeBSD, macOS, and other UNIX-like or POSIX-compliant operating
 		systems. The first six integer or pointer arguments are passed in registers
 		RDI, RSI, RDX, RCX, R8, and R9, while XMM0, XMM1, XMM2, XMM3, XMM4, XMM5,
 		XMM6 and XMM7 are used for floating point arguments. For system calls, R10
diff --git a/arch/sim/src/sim/up_setjmp64.S b/arch/sim/src/sim/up_setjmp64.S
index 7a52c11d78..7e958c0826 100644
--- a/arch/sim/src/sim/up_setjmp64.S
+++ b/arch/sim/src/sim/up_setjmp64.S
@@ -57,7 +57,7 @@
 #  define REGS %rcx
 
 /* The calling convention of the System V AMD64 ABI is followed on Solaris,
- * Linux, FreeBSD, Mac OS X, and other UNIX-like or POSIX-compliant operating
+ * Linux, FreeBSD, macOS, and other UNIX-like or POSIX-compliant operating
  * systems. The first six integer or pointer arguments are passed in registers
  * RDI, RSI, RDX, RCX, R8, and R9, while XMM0, XMM1, XMM2, XMM3, XMM4, XMM5,
  * XMM6 and XMM7 are used for floating point arguments. For system calls, R10
diff --git a/boards/arm/am335x/beaglebone-black/scripts/Make.defs b/boards/arm/am335x/beaglebone-black/scripts/Make.defs
index 272d89c8c4..1d87fe46d9 100644
--- a/boards/arm/am335x/beaglebone-black/scripts/Make.defs
+++ b/boards/arm/am335x/beaglebone-black/scripts/Make.defs
@@ -41,7 +41,7 @@ include ${TOPDIR}/arch/arm/src/armv7-a/Toolchain.defs
 
 LDSCRIPT = sdram.ld
 
-# Setup for Windows vs Linux/Cygwin/OSX environments
+# Setup for Windows vs Linux/Cygwin/macOS environments
 
 ifeq ($(WINTOOL),y)
   # Windows-native toolchains
diff --git a/boards/arm/samv7/same70-xplained/README.txt b/boards/arm/samv7/same70-xplained/README.txt
index e009bc62d3..ba085371a0 100644
--- a/boards/arm/samv7/same70-xplained/README.txt
+++ b/boards/arm/samv7/same70-xplained/README.txt
@@ -1087,7 +1087,7 @@ Debugging
 
   This is a simple command line utility for programming ARM-based MCUs
   (currently only Atmel) though CMSIS-DAP SWD interface. It works on Linux,
-  Mac OS X and Windows.  Very useful to around especially if you have the
+  macOS and Windows.  Very useful to around especially if you have the
   following issue:
 
   Booting to FLASH or the ROM Bootloader
diff --git a/boards/arm/stm32/stm32vldiscovery/README.txt b/boards/arm/stm32/stm32vldiscovery/README.txt
index 469699df49..80499e2561 100644
--- a/boards/arm/stm32/stm32vldiscovery/README.txt
+++ b/boards/arm/stm32/stm32vldiscovery/README.txt
@@ -215,4 +215,4 @@ Where <subdir> is one of the following:
 
     Default toolchain:
 
-    CONFIG_ARMV7M_TOOLCHAIN_CODESOURCERYL=y  : CodeSourcery under Linux / Mac OS X
+    CONFIG_ARMV7M_TOOLCHAIN_CODESOURCERYL=y  : CodeSourcery under Linux / macOS
diff --git a/boards/avr/at32uc3/avr32dev1/README.txt b/boards/avr/at32uc3/avr32dev1/README.txt
index 685a8cc830..6d18e27049 100644
--- a/boards/avr/at32uc3/avr32dev1/README.txt
+++ b/boards/avr/at32uc3/avr32dev1/README.txt
@@ -112,7 +112,7 @@ PA17 and PA23 are available from the AVR32DEV1:
 Development Environment
 ^^^^^^^^^^^^^^^^^^^^^^^
 
-  Linux, Mac OS X or Cygwin on Windows can be used for the development environment.
+  Linux, macOS or Cygwin on Windows can be used for the development environment.
   The source has been built only using the GNU toolchain (see below).  Other
   toolchains will likely cause problems. Testing was performed using the Cygwin
   environment.
@@ -142,7 +142,7 @@ WinAVR:
 
 AVR32 Toolchain Builder:
 
-  A third option is to build the toolchain yourself. For OS X and Linux systems,
+  A third option is to build the toolchain yourself. For macOS and Linux systems,
   this Makefile will build a complete gcc-4.4.3 toolchain:
 
     https://github.com/jsnyder/avr32-toolchain
diff --git a/boards/avr/at90usb/micropendous3/README.txt b/boards/avr/at90usb/micropendous3/README.txt
index 2891925269..614dd82e3b 100644
--- a/boards/avr/at90usb/micropendous3/README.txt
+++ b/boards/avr/at90usb/micropendous3/README.txt
@@ -241,9 +241,9 @@ Linux:
   After configuring NuttX, make sure that CONFIG_AVR_LINUXGCC_TOOLCHAIN=y is set in your
   .config file.
 
-Mac OS X:
+macOS:
 
-  For Mac OS X, the CrossPack for AVR toolchain is available from:
+  For macOS, the CrossPack for AVR toolchain is available from:
 
     http://www.obdev.at/products/crosspack/index.html
 
diff --git a/boards/avr/at90usb/teensy-2.0/README.txt b/boards/avr/at90usb/teensy-2.0/README.txt
index f4567604d4..3bab023491 100644
--- a/boards/avr/at90usb/teensy-2.0/README.txt
+++ b/boards/avr/at90usb/teensy-2.0/README.txt
@@ -250,9 +250,9 @@ Linux:
   After configuring NuttX, make sure that CONFIG_AVR_LINUXGCC_TOOLCHAIN=y is set in your
   .config file.
 
-Mac OS X:
+macOS:
 
-  For Mac OS X, the CrossPack for AVR toolchain is available from:
+  For macOS, the CrossPack for AVR toolchain is available from:
 
     http://www.obdev.at/products/crosspack/index.html
 
diff --git a/boards/avr/atmega/amber/README.txt b/boards/avr/atmega/amber/README.txt
index dd7cc4b919..13402498a6 100644
--- a/boards/avr/atmega/amber/README.txt
+++ b/boards/avr/atmega/amber/README.txt
@@ -228,9 +228,9 @@ Linux:
   After configuring NuttX, make sure that CONFIG_AVR_LINUXGCC_TOOLCHAIN=y is set in your
   .config file.
 
-Mac OS X:
+macOS:
 
-  For Mac OS X, the CrossPack for AVR toolchain is available from:
+  For macOS, the CrossPack for AVR toolchain is available from:
 
     http://www.obdev.at/products/crosspack/index.html
 
diff --git a/boards/avr/atmega/moteino-mega/README.txt b/boards/avr/atmega/moteino-mega/README.txt
index c4eee8758b..86bdf09b23 100644
--- a/boards/avr/atmega/moteino-mega/README.txt
+++ b/boards/avr/atmega/moteino-mega/README.txt
@@ -123,7 +123,7 @@ the toolchain on the make commandline with CONFIG_AVR_TOOLCHAIN=<toolchain>.
 
 The valid values for <toolchain> are BUILDROOT, CROSSPACK, LINUXGCC and WINAVR.
 
-This port was tested using the OS X / CROSSPACK tool chain, GCC version 4.8.1.
+This port was tested using the macOS / CROSSPACK tool chain, GCC version 4.8.1.
 Please see other NuttX documentation for toolchain details.
 
 MoteinoMEGA Configuration Options
diff --git a/boards/mips/pic32mx/mirtoo/README.txt b/boards/mips/pic32mx/mirtoo/README.txt
index ec0ba3331f..8704948e44 100644
--- a/boards/mips/pic32mx/mirtoo/README.txt
+++ b/boards/mips/pic32mx/mirtoo/README.txt
@@ -395,7 +395,7 @@ Toolchains
   mips-elf toolchain:
 
     CONFIG_MIPS32_TOOLCHAIN_PINGUINOW - Pinguino mips-elf toolchain for Windows
-    CONFIG_MIPS32_TOOLCHAIN_GNU_ELF   - mips-elf toolchain for Linux or OS X
+    CONFIG_MIPS32_TOOLCHAIN_GNU_ELF   - mips-elf toolchain for Linux or macOS
 
   And set the path appropriately in the PATH environment variable.  These tool
   configurations are untested -- expect some additional integration issues.