Uncertain, 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. Other suggested derivations include corruptions of French l'eau (“water”), lieu (“place”), lieux d'aisances (“'places of convenience': a lavatory”), lieu à l'anglaise (“'English place': a British-style lavatory”), bordalou (“a diminutive chamber pot”) or gardez l'eau (“'mind the water'”), via Scots gardyloo, formerly used in Edinburgh while emptying chamber pots out of windows; the supposed use of "Room 100" as the lavatory in Continental hotels; 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; 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 name-card was placed on the door to the lavatory, prompting the other guests to begin speaking of "going to Lady Louisa".
I suppose it is unreal because we have been expecting it [sc. World War II] for so long now, and have known that it must be got over before we can go on with our lives. Like in the night when you want to go to the loo and it is miles away down a freezing cold passage and yet you know you have to go down that passage before you can be happy and sleep again.1940, Nancy Mitford, chapter II, in Pigeon Pie, page 27:
Ensure that the tents are well-sited and clean, rubbish bins empty, and that the loos have toilet paper.2006, Garth Thompson et al., The Guide′s Guide to Guiding, 3rd edition, page 160:
The lack of running water in rural areas often makes Western-style loos hygienic disasters. Suddenly the noncontact squat toilet doesn′t look like such a bad option any more (as long as you roll up your trouser legs).2009, Katharina Kane, Lonely Planet: The Gambia and Senegal, page 275:
Waterless urinals are a great way of keeping the guys out of the cubicle toilets, keeping the urine separated from the solid waste (when using composting loos) and reducing water consumption if you have flush loos.2010, Meegan Jones, Sustainable Event Management, page 206:
Edg. Pilicock sate on pelicocks hill, a lo lo lo.c. 1603–1606, William Shakespeare, “The Tragedie of King Lear”, in Mr. William Shakespeares Comedies, Histories, & Tragedies […] (First Folio), London: […] Isaac Iaggard, and Ed[ward] Blount, published 1623, →OCLC, [Act I, scene xi]:
Dialectal, Used with at To urge on with cries of loo or (figuratively) by other shouting or outcry.
Upon or infinitive
And therefore next uncouple either Hound [sc. George Monck and Prince Rupert], And loo them at two Hares ere one be found.1667, John Denham, Directions to a Painter, ll. 21 f:
loo
noun
Etymology Clipped form of lanterloo.
1
Alternative Alternative form of lanterloo: the card game.
And my Intreagues ſo baſhfully diſown / That they may doubted be by few or none, / May kiſs the Cards at Picque, Hombre,—Lu, / And ſo be taught to kiſs the Lady too; [...]1675, [William] Wycherley, The Country-wife, a Comedy, […], London: Printed for Thomas Dring, […], →OCLC; republished London: Printed for T[homas] Dring, and sold by R. Bentley, and S. Magnes […], 1688, →OCLC, epilogue:
Ev'n mighty Pam that Kings and Queens o'erthrew, And mow'd down Armies in the Fights of Lu.1712 May, [Alexander Pope], “The Rape of the Locke. An Heroi-comical Poem.”, in Miscellaneous Poems and Translations. […], London: […] Bernard Lintott […], →OCLC, canto III:
2 more examples
Yet, ladies are seldom at ombre or lue sick.1731, Jonathan Swift, To Dr. Helsham, 16
On entering the drawing-room, she found the whole party at loo.1813 January 27, [Jane Austen], chapter VIII, in Pride and Prejudice: […], volume I, London: […] [George Sidney] for T[homas] Egerton, […], →OCLC, page 80:
2
The penalty paid to the pool in lanterloo for breaking certain rules or failing to take a trick.
Etymology From French loup (“wolf; mask, eyemask”). Doublet of lobo, lupus, and wolf.
1
Fashion, LifestyleObsolete A half-mask, particularly (historical) those velvet half-masks fashionable in the 17th century as a means of protecting women's complexion from the sun.
Loo Mask. An half Mask.a. 1685, Mary Evelyn, “The Fop-dictionary”, in Mundus Muliebris, page 18:
Etymology From Hindi लू (lū), ultmately from Sanskrit उल्का (ulkā, “flame”).
1
India A hot dust-bearing wind found in Bihar, Uttar Pradesh and the Punjab.
It was a pitchy black night, as stifling as a June night can be, and the loo, the red-hot wind from the westward, was booming among the tinder-dry trees and pretending that the rain was on its heels.1888, Rudyard Kipling, “The Man Who Would Be King”, in The Phantom 'Rickshaw and Other Tales, page 78:
I asked my loo to let me escort you in. I wanted a moment to thank you personally.” “There's no need.” “So you said before, but there is. And was. I'll take you in to Lieutenant Ricchio.”2012, J. D. Robb, New York to Dallas, Penguin, →ISBN, page 91: