A pedantic correction: "gender" appears to have had that non-grammatical meaning since the 15th century (and has also had an NSFW meaning as a verb since even earlier) but (if the OED is to be trusted, which usually it is) it's true that "gender" became widely used to mean males/females collectively in the 20th century because "sex" was too distracting. (It wasn't "sex" as a verb, though, but "sex" as a noun meaning "copulation".)
This thread is for asking any questions that might seem obvious, tangential, silly or what-have-you. Don't be shy, everyone has holes in their knowledge, though the fewer and the smaller we can make them, the better.
Please be respectful of other people's admitting ignorance and don't mock them for it, as they're doing a noble thing.
To any future monthly posters of SQ threads, please remember to add the "stupid_questions" tag.