quinella Look up quinella at Dictionary.com
form of betting in which the bettor picks the first and second horses in a given race, 1942, Amer.Eng., from Amer.Sp. quiniela, originally a ball game with five players, from L. quini “five each,” from quinque “five” (see quinque-). The sense evolution in Spanish was from the game to a wager on the scores of the players, hence “any wager against the house.”
Which doesn’t really explain why this term applied to that particular form of wager.
I was just thinking of this the other day when I saw “exacta” in Dave’s list.
EDIT: what an interesting world of words it is when an American Spanish word for one thing can become an English word for something else that no one outside of NZ/Aust has ever heard of, in such a short space of time.