Obviously through PORN, or osmosis, or something. I must've figured it out halfway through high school, and since then I've been getting myself in the somewhat uncomfortable position of assuming that everyone knows what it means, alluding to it, and then having to explain. :D (Also, link (http://www.lorebrandcomics.com/newtrend.html).)

Maybe the manga, but not (most of) the fic I read (outside of PoT). :/