Jason Kottke did a little research on just that query and the while the jury is still out, the possible theories are all plausible.
He says," When I was in London a couple of weeks ago, a group of us was sitting around in a pub on Saturday afternoon (what a cliché!) and someone mentioned that the reason that the English "loo" is so named because the toilet was commonly located in room 100 of buildings and the two ("loo" and "100") look very much the same."
He also unearthed the following other possibilities:
When people flung their potty waste out of the window, they would shout "Gardez l'eau" [gar-day low]. That's French for "watch out for the water". - History of Loos
"The word appears to originate no earlier than James Joyce's usage in Ulysses in 1922 -- "O yes, mon loup. How much cost? Waterloo. water closet." -- perhaps Joyce came up with it. Or it could be "a British mispronunciation of the French le lieu, "the place", a euphemism." - Michael Quinion
"It's short for "Lady Louisa," Louisa being the unpopular wife of a 19th-century earl of Lichfield. In 1867 while the couple was visiting friends, two young wiseacres took the namecard off her bedroom door and stuck it on the door of the bathroom. The other guests thereafter began jocularly speaking of "going to Lady Louisa." In shortened form this eventually spread to the masses." - Cecil Adams
Kottke wraps up: "But Adams has no definitive answer either and so the question of the etymology of loo will continue to be debated on the Internet and in pubs around the world."
Via: kottke.org
"Gardy-loo!" is an Edinburgh thing - the Old Town was built on such a tiny, constricted scrap of land that we ended up building the first skyscrapers (well, we got up to 12 or 13 stories). People were too lazy to go down all those flights of stairs so they'd chuck the contents of their chamber pot out of the window instead and shout a warning, as you explained. I'm an Edinburgh girl and that's the explanation I'm sticking to!
(Btw, I think they were pulling your leg about the "100" thing... ;) )
view Laurita's profile
My English boyfriend told me that he didn't know why it was called the loo, but said it sounds nicer then saying 'I have to go to the bathroom, or toilet, or restroom'.
and I agree, it does sound nicer.
view Jamie's profile
I've heard the "Garde-Loo" thing too - I heard it was a hold over from when parts of England were still french speaking. Before chucking the chamber pot out the window you would yell "Gardez Lui" - or, loosely translated, "Look out"
view Neujeramic's profile
Yes to pulling your leg about the 100 thing - also to whoever told Neujeramic that parts of England used to be French speaking...
view Lesley - London's profile
I've heard the Lady Louisa explanation before.
view Christine (the one in DC)'s profile
Loo comes from a early brand of toilet cistern called "waterloo", same as crap came from Thomas Crapper who invented the flushing loo!
view james79's profile
I'd bet on the "Gardy-loo" option.
It's actually the French phrase "Gardez l'eau" - essentially "watch the water", translated watch out for the 'water' coming from above. The 'water' was all manner of household waste dumped from upper floors. Yuck.
view Gursk's profile
Weren't parts of England French-speaking when William of Normandy came over the English Channel, defeated two other claimants to the English throne, and became William the Conqueror? Because he and his court were French, or so I learned in just about any international history class I've ever taken, French was the language of politics and business for centuries in England.
view eaevansmd's profile
Yep, and the court of Mary Queen of Scots all spoke French too - French was the language of Scottish nobles for centuries (which isn't to say they didn't also speak Scots and/or Gaelic).
view El Jinx's profile
Loo is definitely an Englishization of "L'Eau" or the water. Funnily, the french call their bathroom the "WC" which is an abbreviation for "Water Closet." So the English prefer to use a French word for bathroom, while the French prefer to use an English word. Hee.
view Miriam's profile
PS the OED gives a number of meanings of "loo," concluding that Joyce's text is the first time the word appeared in print. But here are some of the other definitions:
1. The "pool" in a 19th century card game (presumably from 'L'eau").
2. In the 1690s, a ladies' velvet mask covering the upper part of the face
3. A cry to hunting hounds (Haloo! Loo loo!)
PS I've also always wondered about "Waterloo"- isn't that just saying "Water Water" first in English then in French? Or is it Water-place (Water-lieu)?
view Miriam's profile
I've been waiting for this. I didn't echo the word "parts" at all well and wrote too quickly, I meant to respond to the implication (which is probably not even there) that all England had been French speaking at some point. I wanted to re-write as soon as I'd commented - so serves me right. No offence meant.
So now I look like an eejitt as clearly William the Conquerer was from Normandy and the administrative and legal language was French - and the English spoken throughout that period by the Saxons (if not by the invaders) developed from Old English (Germanic influence) to Middle English (French influence). And now I just look like a boring eejitt. Which would be fair.
My personal view, is the same as Laurita's - Gardy Loo/Gardez l'eau is an Edinburgh thing. Lots of more recent French associations in Scotland. And I should have left it at that.
view Lesley - London's profile