My assumption for the key icon was something to do with PINs/passkeys, which kind of reinforces OP’s point.

Ngl I really want to know what the tick icon actually does now.

And “a11y” is the most obscure – dare I say… inaccessible – fucking abbreviation of “accessibility”. For years I only saw them in passing and assumed both these things were like, quirkily-named Javascript frameworks or niche standards documents or something, despite knowing quite well the concepts they actually refer to.