'maxOS' is Apple's current name for the Mac operating system.  See https://en.wikipedia.org/wiki/MacOS, Contents, Release History.

The module name macosx.py is currently left as is.  Within that, 'Mac OS X' is correct for 10.6 for 10.8.

This issue is a spinoff of #34864.

@terry, I suppose you wanted to say "macOs" and not "maxOs"

Whoops, 'macOS', as in the title and PR.

;-) just a joke.

I have reviewed your PR, but do you count with the occurences of "OS X", it's the abbreviation of "MacOS X"?

The history of names for 10.X, from the reference above (which also has nicknames, like 'Mavericks' and 'Mohave', which I believe we do not use).

10.0 to 10.7: Mac OS X (space or spaces sometime left out, as in macosx)
10.8 to 10.13: OS X (2012, ditto)
10.14 to (current) 10.16 (2016)

AFAIK, the current Mac installers support either 10.6+ or 10.9+.  The macosx references to 'Mac OS X 10.6' and 'OS X 10.7 and 10.8' are properly not changed.

'OS X' in pyshell.py is removed in PR 10464.

The most recent item in NEWS.txt using 'OS X' is for #27310, June 2016, by Ned, who used 'OS X'.  So no changes to NEWS.txt or NEWS2.txt.

** Ned **
Should 'OS X Aqua Tk' be changed to 'macOS Aqua Tk' or 'macOS (OS X) Aqua Tk'?  In other words, is 'OS X' here a replaceable noun adjective or an integral part of a proper name?  The PR did the 2nd replacement in config.py, since the comment is about the 'IDLE Classic OSX' keyset, but I deferred the change in mainmenu.py.

Same issue with 'OS X Cocoa Tk 8.5' in editor.py.

Editor.py also has "Some OS X systems have only one mouse button".  It seems to me that 'Mac' would be a better replacement that 'macOS' as the mouse is part of the hardware system, not the OS software.

The 4th line above should include 'macOS'.

10.14 to current 10.16: macOS (2016)

New changeset b65413b497a07f521d835b799be7dd0afcedbd65 by Terry Jan Reedy in branch 'master':
bpo-35213: Where appropriate, use 'macOS' in idlelib. (#10478)
https://github.com/python/cpython/commit/b65413b497a07f521d835b799be7dd0afcedbd65

New changeset 579c4175648f667d59954d48ada757621ff6d433 by Miss Islington (bot) in branch '3.7':
bpo-35213: Where appropriate, use 'macOS' in idlelib. (GH-10478)
https://github.com/python/cpython/commit/579c4175648f667d59954d48ada757621ff6d433

New changeset be657c1fac3ce436976541cf2680a977217be813 by Miss Islington (bot) in branch '3.6':
bpo-35213: Where appropriate, use 'macOS' in idlelib. (GH-10478)
https://github.com/python/cpython/commit/be657c1fac3ce436976541cf2680a977217be813

Any more changes can be a future issue.