Green’s Dictionary of Slang

the world of street prostitution.

1946		G. Kersh Nigth and the City 122: Anybody would think I was asking you to go on the bash, or something. You can keep respectable in a night club.
1959		B. Naughton ‘The Little Welsh Girl’ in Late Night on Watling Street (1969) 144: We could have sent her out on the bash ourselves.
1963		F. Norman in Show Jan. in Norman’s London (1969) 1443: They take the birds orf the bash [...] and then expect them to settle darhn and get job in offices and that.
1967		T. Parker Women in Crime 75: Well when I come out [of prison] I’ll have nothing, so the quickest way to get a bit of money is to go on the bash for it.