Where did WIN32_LEAN_AND_MEAN come from? - The Old New Thing devblogs.microsoft.com

Raymond Chen says `WIN32_LEAN_AND_MEAN` was introduced around the Windows 95 transition to 32-bit Windows, so `windows.h` could omit headers and retain the minimal-inclusion approach of 16-bit Windows. On a 50 MHz 80486, he recalls it cutting about three seconds from each C file’s compile time; faster computers and precompiled headers have since made the savings negligible.