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.
Ohh I always thought "apropos" was from the French expression "à propos (de)... " which means "about". I naïvely believed that the person who coded this command must be French.
The English usage is borrowed from French![0] However, it doesn't look like the original author was French[1]. I shouldn't be, but I am quite surprised to see that the apropos command as we know it is 43 years old!