What is a plausible etymology of "dosh", a British slang word for money?

Neither Wiktionary nor The Online Etymology Dictionary seem to know anything.

UPDATED (October 25 2015)

dosh ‎(uncountable)

  1. (Britain, slang) Money

Etymology Unknown. Possibly a combination of dough and cash
Wiktionary


Chambers Dictionary 11th Ed.:

ORIGIN: Poss *do*llars and ca*sh*

Partridge Dictionary of Slang:

Possibly a combination of dollars and cash; there are also suggestions that the etymology leads back to doss (temporary accommodation), hence, it has been claimed, the money required to doss, or Scottish dialect doss (tobacco pouch, a purse containing something of value) – note, too, that tobacco is related to money via quid. US dosh didn’t survive but in mid-C20 UK and Australia the word was resurrected, or coincidentally recoined US, 1854

Oxford Advanced Learner’s Dictionary 8th Ed.:

1950s: of unknown origin

Oxford English Dictionary:

Origin unknown.

1953 H. Clevely Public Enemy xviii. 114 He hadn't enough dosh on him.


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":

dosh n British[:] money. This is a working-class term from the early 1950s which was falling out of use in the 1960s, but which, like many similar words (bunce, loot, lolly, etc.), was revived in the money conscious late 1980s. It is a favourite with alternative comedians and 'professional cockneys'. The original would seem logically to be the old African colonial term dash, denoting a tip or bribe, but other authorities claim that it is influenced by doss [defined in its own entry as meaning "a place to sleep," "a period of sleep," or "a very easy task"], in the sense of the price of a bed (for the night).

John Ayto & John Simpson, The Oxford Dictionary of Modern Slang (1992), meanwhile, stick to the OED line of "origin unknown":

dosh noun Money 1953–. ** 'America! The money's in America!' ... ''Tis true. The Yankees have the dosh all right' (1970) {Origin unknown}