it's where gentlemen went after a meal to smoke - 'drawing' being a description of inhalation of breath
I think that's where it comes from - though I'm not certain
 a quick search on google, actually puts me wrong, and it's a shortened version of 'withdrawing room' - ie somewhere you can withdraw to, either after a meal, or a place to take guests into as they enter the house. [/edit]
Edited 1 times. Last edit at 6 January 2005 4.01pm by JonR.
Surely you're aware that all the best people now have a full suite of Roman Baths with tepidarium (warm room), caldarium (hot room) and fridgidarium (cold plunge pool). And if you use it for entertaining, an apodyterium (dressing room).