Loo
1940s: many theories have been put forward about the word's origin: one suggests the source is Waterloo, a trade name for iron cisterns in the early part of the century; the evidence remains inconclusive.
wiktionary
Clipped form of halloo. [1]
Clipped form of lanterloo. [2]
From French loup(“ wolf; mask, eyemask”). [3] Doublet of wolf.
From Hindi उल्का(ulkā), from Sanskrit उल्का(ulkā, “ flame”). [4]
Of uncertain etymology, although usually derived in some way from Waterloo, the site of Wellington's 1815 victory over Napoleon, likely via a pun based on water closet. [5] [6] [7] [8] [9] [10] Other suggested derivations include corruptions of French l' eau(“ water”), [7] lieu(“ place”), [7] [10] [11] lieux d'aisances(“' places of convenience': a lavatory”), [8] [9] [12] lieu à l' anglaise(“' English place': a British -style lavatory”), bordalou(“a diminutive chamber pot”) [7] or gare l' eau(“' mind the water'”), via Scots gardyloo, formerly used in Edinburgh while emptying chamber pots out of windows; [7] [10] [13] [14] the supposed use of "Room 100" as the lavatory in Continental hotels; [6] [10] a popularisation of lew, a regional corruption of lee(“ downwind”), in reference to shepherds' privies or the former use of beakheads on that side of the ship for urination and defecation; [7] [15] [11] [8] or a clipped form of the name of the unpopular 19th-century Countess of Lichfield Lady Harriett Georgiana Louisa Hamilton Anson, who was the subject of an 1867 prank whereby her bedroom's namecard was placed on the door to the lavatory, prompting the other guests to begin speaking of "going to Lady Louisa". [10] [16]
Clipped form of lieutenant.
etymonline
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.
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.
