Proper noun: Pretentious form of Colliers Wood, a naff suburb of south west London. Pronounced with a perfect French accent (bwa de coll-yay) and used in a mocking way about people who live there and overrate the place. See also Croùch End, Battercia, Pengé.
"You're from Wimbledon? My English friend lives in Bois de Colliers! Maybe you know her."
"Actually, I never mix with fatuous, social-climbing champagne socialists.