Green’s Dictionary of Slang

1. a criminal; usu. in combs. such as badger worker under badger n.¹ , charity worker under charity n., dunnigan (worker) under dunnaken n., lush worker under lush n.¹ , skin worker under skin n.¹ , tail worker under tail n.

1897		Eldridge & Watts Our Rival, the Rascal 276: One of the most notable thieves of this class in the country is Charles Spencer [...] About twelve years ago he applied himself particularly to the occupation of a ‘sleeping car worker.’ Here he soon earned a reputation as ‘the fastest worker in the country in his line’.
1900		Nat. Police Gaz. (NY) 24 Feb. 3/1: There are usually three cappers employed by the successful worker in soap goods.
1927		C. Drew ‘Grafter and Goose’ in Bulletin (Sydney) 11 Aug. n.p.: [of confidence tricksters] [T]he racecourse detectives, [...] are ever on the watch for ‘workers’.
1935		G. Ingram Cockney Cavalcade 256: ‘Finger-prints!’ the detective said in contempt. ‘No. It was too good for most of those that do that sort of job. That’s why I thought you might know something about it. You’re such a pretty worker.’.
1955		Q. Reynolds Police Headquarters (1956) 77: Bonwit Teller has had a series of pocketbook robberies. The character who is getting away with these bags [...] goes into the ladies room [...] ‘Toilet workers — Female.’.
1975		‘P.B. Yuill’ Hazell and the Three-card Trick (1977) 78: You take a real worker — one ov the fanny mob or a cracksman or even a dip, anybody wiv a bit ov class, he’ll tell yer.

2. in a pickpocket team, the member who actually picks the victim’s pocket.

1914

W. Sickert New Age 19 Mar. 631: All these he would carry with him so that he, the ‘worker,’ or the ‘tool,’ might have his mind and his hands freed for the masterstroke.