J, n. A consonant in English, but some nations use it as a vowel . . . from a Latin verb, jacere, to throw, because when a stone is thrown at a dog the dog's tail assumes that shape.
Source: The Devil's Dictionary, 1911.
-- Ambrose Bierce, (Jun 24 1842-1914), US journalist, short-story writer; He was a noted wit, satirist and sardonic short story writer who disappeared while covering the Mexican revolution.