I used to have a hard time remembering apropos because I assumed 'apropos' was some sort of unixy mincing of another word or abbreviation or something, and I couldn't figure out what it meant. You know, like 'mkdir' means "MaKe DIRectory"

But it turns out apropos is just a regular word. Once I learned this, I haven't had any more trouble with it.

apropos : Of an appropriate or pertinent nature.

https://en.wiktionary.org/wiki/apropos