Green’s Dictionary of Slang

(UK Und.) a mendicant villain who used his abilities of reading and writing to forge counterfeit begging licences.

c.1561		Awdeley Fraternitye of Vacabondes in Viles & Furnivall (1907) 5: A Iackman is he that can write and reade, and sometime speake latin. He vseth to make counterfaite licenses which they call Gybes, and sets to Scales, in their language called Iarkes.
1608		Dekker Belman of London D3: Therefore are there some in this Schoole of Beggars that practice writing and Reading, and those are called Iackemen [...] Yea the Iackman is so cunning sometimes that he can speake Latine: [...] by that means he becomes Clarke of their Hall, and his office is to make counterfeit licences.
1621		Jonson Gypsies Metamorphosed 3: [stage direction] A Gipsie leading a horse laden with five little children [...] The first leading Gipsie speakes beeing the Jackman.
1669		W. Winstanley New Help To Discourse 133: Jack-men, are such as can write and read, whose office it is to make counterfeit Licenses and Passes, for which he is well rewarded of them.
1674		Head Canting Academy (2nd edn) 57: [as cit. 1669].
1688		R. Holme Academy of Armory Ch. iii item 68b: Give me leave to give you the names (as in their Canting Language they call themselves) of all (or most of such) as follow the Vagabond Trade, according to their Regiments or Divisions, as [...] Jackmen, Counterfeiters.
1707		J. Shirley Triumph of Wit 182: The Jack-man is their Secretary, who having some small Abilities in Learning, especially in Writing and Counterfeiting of Hands, makes it his Business to write their false Passes, false Certificates, and Maunding Letters, and is in great Esteem amongst them.
1785, 1788, 1796		Grose Classical Dict. of the Vulgar Tongue.
1811		Lex. Balatronicum.
1856		‘A Harassing Painsworth’ in Yates & Brough (eds) Our Miscellany 28: Listen! all you high pads and low pads, rum gills and queer gills, patricos, palliards, priggers, whipjacks, and jackmen, from the arch rogue to the needy mizzler.