So we were at a scholastic bowl meet one day in our senior year of high school, and we were given the toss-up "What is one minus cosine x?" None of had any clue. We all had gone thru pre-calc and were fairly well versed in trig identities, but this just didn't seem to go anywhere. I do believe that Dave, our local math genius, answered "sin squared x" out of desperation (there might have been a typo, it is fairly common, and there's no penalty for guessing). After the allotted time was up, the moderator announced the answer as "versine." Ok, that's odd: we're all on Math Team, and we have never heard of this, so we ask him how it is spelled, and indeed, it is: "v-e-r-s-i-n-e", which doesn't seem likely to be a typing mistake or a result of the moderator being dumb. We were all baffled.

The next day, we went to our esteemed Calculus teacher, Mr. Neumer, and asked him if he has ever heard of it. Amazingly enough, he had. He said it was something mathematicians in the 13th century (or something) had invented because they thought that it was going to be useful. Later, the idea was scrapped when people realized it was useless. And to make this more clear, he drew some kind of wavy line on the board to represent mathematical progress vs. time (approximation shown here), where the versine was invented in one of the low spots.

So we found out what versine is. Mr. Nuemer, in his explanation, however, does not stop there. He goes on to say that versine is stupid because it is no more useful than sticking any other random functions together and giving it a new name. He says, "For instance, I could just say..." and he writes "quadong(x) = tan2(x) - e" and the board, "and then freshmen will walk by and say 'WOW! That really is an advanced math class! They're already on quadongs!'" We were amused and the word stuck.

So that is quadong. Pretty exciting, no?

Note: versine is not actually defined in Mathematica, but Wolfram notes its existance: see this, towards the bottom.