Here are a few more things I've learned about our language lately.
Deceit of lapwings: In Lynn Shepherd's novel A Fatal Likeness, Charles Maddox remembers as a boy asking his father why a gathering of lapwings was called a deceit. It seemed like such an awful word for such pretty birds. His father explains that the word had originally been desert, but that it had been corrupted over time to deceit. "Because parent lapwings will abandon their nest to lead predators astray -- protecting their young in the very act of appearing to forsake them." Of course, as Charles observes, that makes deceit also a very fitting term.
Penguin: Henry Hitchings explains in The Secret Life of Words that the word penguin is a composite of two Welsh words meaning "white" and "head." This is odd, he observes, because penguins have black heads.
Whisky: The Gaelic word usquebaugh was "viley corrupted" by the Saxons into the word whisky, A.J. Cronin writes in his memoir Adventures in Two Worlds. I have used the spelling of the word Cronin uses in his book.The Oxford American Dictionary tells me the word is spelled whiskey for American and Irish products, but whisky for Scotch and Canadian products. Cronin hailed from Scotland, although he lived a good part of his life in England and the United States.
Sleep tight: This odd expression, which so many of us have used, especially when putting children to bed, dates from the era of feather beds, which tended to sag to the point where they became a lot less comfortable than they looked. To correct the problem it was necessary to tighten the lattice of ropes under the bed. Bill Bryson reports this in At Home.