UPDATED (October 25 2015)
- (Britain, slang) Money
Etymology Unknown. Possibly a combination of dough and cash
Chambers Dictionary 11th Ed.:
Partridge Dictionary of Slang:
Oxford Advanced Learner’s Dictionary 8th Ed.:
Oxford English Dictionary:
Tony Thorne, The Dictionary of Contemporary Slang (1990) repeats one of the origin theories that Partridge notes (as quoted in user3286's answer), but also suggests an alternative involving "the African colonial term dash":
John Ayto & John Simpson, The Oxford Dictionary of Modern Slang (1992), meanwhile, stick to the OED line of "origin unknown":
DOSH = bangla for TEN that's where it comes from. It was picked up during the time when the The British East India Company was running the show out there, just like CHA was picked up for tea.
I just don't think that it could possibly came from doss house. It is an Americanized german word of Dosch
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