Green’s Dictionary of Slang

1. a dice cheat.

1552

G. Walker Detection of Vyle and Detestable Use of Dice Play 28: But it is enough at this time to put you in a remembrance what tools ye must prepare to make you a workman.

2. a card-sharp.

1829		Vidocq Memoirs (trans. W. McGinn) III 17: We know well enough that you are a fellow workman, but you are a deep file: we two might do a fine stroke of business.
1903		A. Binstead Pitcher in Paradise 184: I’d rather drop a few thousands to Bob Sinclair than I’d get it off of some of the burglars [...] that passes for workmen nowadays.

3. (UK Und.) a pickpocket.

1912

E. Pugh City Of The World 276: Then they got more artful and clever. They chummed up with real swell workmen that passed things to ’em in a crowd.