Arson. The idea that someone, years ago, had to come up with a name to give the crime of causing a premeditated fire to a building for some type of personal gain, and then came up with a word that sounds like some dude's name is, hilarious to me. Arson itself isn't funny (okay, maybe a little), but the word sure is.
Asinine. It's a fancy way of saying an idea is incredibly idiotic, but apparently it's used so little that it can be mistaken for a swear. The people that worked on the clean version of Eminem's "Relapse" blanked it not only once, but then again on his next album "Recovery." Nowadays, I try to use it as much in conversation as possible.
Jaime_Wolf said:
If by "wait, there's actually a unique word for that?":
"Fenestrate". Every kid who's heard of the Defenestration of Prague knows that that "defenestration" is one of the better weird words lying around in the dustier corners of English, but "fenestration" is just absurd. Being thrown out of a window is one thing and we see it happen often enough in fiction alone to make the word slightly reasonable, but how often do you see people thrown into windows.
Thanks for adding another awesome word to my vocab.