Let's start with a declaration: curmudgeon may be my favourite word in English. Here's why.
First, it condenses so much meaning into a single word. I mean, you could call someone a grumpy old fart, but why bother when curmudgeon is available?
Second, it sounds so right, doesn't it? Consider its first three consonants: a snarling c, followed by a 'sod off' m with a disdainful hard j in hot pursuit. The vowels are something to behold too. A slow wind-up errrr, like Muhammad Ali tauntingly swinging his arm before exploding forth with a vicious one-two, ah-i. It's an ugly, mean, spiteful word that you don't so much say as spit out. How glorious!
Finally, curmudgeon is shrouded mystery: no one knows from whence it came. One theory is that it was borrowed from Gaelic, and another - offered by Samuel Johnson - is that it's a corruption of the French couer mechant, or evil heart. But no one takes either theory seriously. That means someone - probably in the late 1500s - may have simply invented the word out of thin air.
Words of Unknown Origin is a surprisingly large and diverse category within English. It includes not-so-surprising words like ballyhoo, codswallop, fipple, gizmo, jalopy and shebang, but also a whole swag of surprising ones like bet, blight, bloke, cuddle, flare, hunch, jam, piddle, prod, puzzle, quirk, sleazy and toggle. Condom, another word of unknown origin, was omitted from the original Oxford English Dictionary (c. 1890) and was unmentionable in US mass media until 1986, when Surgeon General C. Everett Koop used it in a speech on AIDS prevention. Remember that next time you hear a tut-tutting news item about some allegedly backward country that refuses to get with the AIDS prevention programme.