(author here) Thanks for posting! I need to update/post a follow-up with a couple of notes since I wrote that post:

* Ben van Enckevort, the original creator of the Slack quick-switcher with Ctrl/Cmd-K, showed up in the StackOverflow thread to tell us the choice of "K" was fairly arbitrary: https://ux.stackexchange.com/a/153937 . Thanks AJ Montoya for pointing it out too :)

* Dean Jackson pointed out TextMate as the predecessor to Sublime, including fuzzy search jump-to-file

* Amit Patel suggested Emacs as a potential originator, which led us to find Richard Stallman's manual for Emacs 150 (1980) which does have the Meta-X "extended command" that is very similar to today's command palette. A 1978 TECO manual doesn't mention this, so right around 1980 would be the right time frame.

Why not Alt-x like emacs (should I say Meta-x) ? I'm a big user of sublime text and I find alt-x way more convenient simply because it's very easy to do that shortcut with one hand. Plus the slot is not used by default config.