Etymology
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loo (n.1)
"lavatory," 1940, but perhaps 1922 (based on a pun of Joyce's); perhaps [Dictionary of American Slang] from French lieux d'aisances "lavatory," literally "place of ease," picked up by British servicemen in France during World War I. Or possibly a pun on Waterloo, based on water closet.
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loo (n.2)

type of betting card game involving a hand of three cards, 1670s, short for lanterloo (1660s), from French lanturelu, originally (1620s) the refrain of a popular comic song; according to French sources the refrain expresses a mocking refusal or an evasive answer and was formed on the older word for a type of song chorus, turelure; apparently a jingling reduplication of loure "bagpipe" (which is perhaps from Latin lura "bag, purse").

From its primary signification — a kind of bagpipe inflated from the mouth — the word 'loure' came to mean an old dance, in slower rhythm than the gigue, generally in 6-4 time. As this was danced to the nasal tones of the 'loure,' the term 'loure' was gradually applied to any passage meant to be played in the style of the old bagpipe airs. ["Grove's Dictionary of Music and Musicians," London, 1906]

The refrain sometimes is met in English as turra-lurra. In the game, also the name of the pool or kitty of chips deposited by players before seeing their hands, or of the deposit made in it by a player.

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Waterloo (n.)
village near Brussels; the great battle there took place June 18, 1815; extended sense of "a final, crushing defeat" is first attested 1816 in letter of Lord Byron. The second element in the place name is from Flemish loo "sacred wood" (see lea (n.)).
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lea (n.)
Old English leah "open field, meadow, piece of untilled grassy ground," earlier læch, preserved in place names, from Proto-Germanic *lauhaz (source also of Old High German loh "clearing," and probably also Flemish -loo, which forms the second element in Waterloo), from PIE *louko- "light place" (source also of Sanskrit lokah "open space, free space, world," Latin lucus "grove, sacred grove, wood," Lithuanian laukas "open field, land"), from root *leuk- "to shine, be bright." The dative form is the source of many of the English surnames Lee, Leigh.
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loofah (n.)
1879 (as lough, 1865), from Egyptian Arabic lufah, the name of the plant (Luffa ægyptiaca) with fibrous pods from which flesh-brushes are made.
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loon (n.1)
large diving bird (especially the Great Northern Diver), 1630s, apparently an alteration of loom in this sense, which is from a Scandinavian source (compare Norwegian lom, from Old Norse lomr "loon").
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loof (n.)
"palm of the hand," Scottish and Northern English, c. 1300, from Old Norse lofe "hand," which is said to be cognate with Gothic lofa, Russian lapa "paw," Lettish lepa "paw."
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loogie (n.)
"nasal mucus," U.S. slang, by 1990.
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fast and loose 
described as "a cheating game played with a stick and a belt or string, so arranged that a spectator would think he could make the latter fast by placing a stick through its intricate folds, whereas the operator could detach it at once." [James O. Halliwell, "Dictionary of Archaic and Provincial Words," 1847]. The figurative sense (1550s) is recorded earlier than the literal (1570s).
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loosely (adv.)
late 14c., from loose (adj.) + -ly (2). Similar formation in Dutch losselijk, Old Norse lausliga, Danish löselig.
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