Green’s Dictionary of Slang

heel n.

[? SE down-at-heel or the image of an unwanted person, continually at one’s heels]

1. (US Und.) constr. with the, ‘The racket of stealing by sneaking’ (Sutherland, The Professional Thief, 1937).

implied in on the heel
[US](con. 1905–25) E.H. Sutherland Professional Thief (1956) 18: When the heel is being worked two-handed, the one who is watching will keep up a constant line of talk or blah in order to make the operation seem natural.

2. (orig. US) a petty criminal.

[US]Wash. Times (DC) 14 Sept. 10/4: Heel— A sneak thief.
[US]Jackson & Hellyer Vocab. Criminal Sl. 43: heel [...] an inefficient or pusillanimous pretender to sterling criminal qualifications.
[US]J. Lait Gangster Girl 18: I’ve got as many heelers as I’ve got heels on my payroll.
[US](con. 1905–25) E.H. Sutherland Professional Thief (1956) 6: Two heels (sneak thieves) had got into the stockroom of a high-class jewelry house.
[US]‘Boxcar Bertha’ Sister of the Road (1975) 103: Big Otto [had] served a two-year stretch. Later I found it was for being a sneak thief, a ‘heel’ as they called it.
[US]Monteleone Criminal Sl. (rev. edn).
[US]J. Thompson ‘The Frightening Frammis’ in Fireworks (1988) 127: They just don’t make ’em any sneakier than my Mitch [...] I’ll bet you’re the biggest heel in the world!
[UK]J. Morton Lowspeak 72: Heel – sneak thief.
[US]J. Ridley Love Is a Racket 33: Wesker. Just another con, just another heel grifter.

3. (orig. US) a general derog., esp. a dishonest, untrustworthy person, esp. one who treats women badly.

[US]Jackson & Hellyer Vocab. Criminal Sl. 43: heel [...] An incompetent; an undesirable.
[US]M. West Pleasure Man (1997) Act I: Say, you heel, do you want me to get fined a hundred smackers for lettin’ a wise-guy pull in here wit’out a card?
[US]J. Weidman What’s In It For Me? 98: Three of the seven heels that infested our so-called office were in one corner.
[US]W. Guthrie Bound for Glory (1969) 19: You big slobbery loafin’ heel.
[Can]R. Service ‘Death’s Way’ in Rhymes of a Roughneck 16: Old Man Death’s a lousy heel who will not play the game.
[UK]Wodehouse Jeeves in the Offing 155: Her first husband [...] was a heel to end all heels.
[US] in S. Harris Hellhole 68: He knew he was a heel and all that, but even he wasn’t bad enough to go to bed with a little girl.
[US]‘Jack Tunney’ Split Decision [ebook] Man, I was a heel for not thinking about him first.
[UK]Observer (London) Rev. 23 Oct. 5/4: It makes me feel a bit of a heel for fathering a child.

4. (US Und.) an informer.

[US]O.O. McIntyre New York Day by Day 23 Dec. [synd. col.] The term ‘heel,’ now used, was a crook who squealed.
[US]C.G. Givens ‘Chatter of Guns’ in Sat. Eve. Post 13 Apr.; list extracted in AS VI:2 (1930) 133: heel, n. One who squeals.
[US]Monteleone Criminal Sl. (rev. edn).
[US](con. 1964–8) J. Ellroy Cold Six Thousand 91: Wicked Wendell [...] a rape-o/a shitbird/a heel.

In phrases

bid adieu with one’s heels (v.)

to be hanged.

Dobson’s Dry Bobs n.p.: If his uncle had not stood his very good friend, he had bid his kinefolkes al adew with his heeles, and daunced his last measures upon the gallowes.
on the heel (US Und.)

1. working as a criminal.

[US]G. Bronson-Howard Enemy to Society 235: I wasn’t above usin’ it I kin tell you when I was out on the ‘heel’.
[US]Monteleone Criminal Sl. (rev. edn).

2. till-tapping.

[US]J. Sullivan ‘Criminal Sl.’ in Amer. Law Rev. LII (1918) 890: Thieves who tap store tills [...] when working are said to be ‘out on the Heel’.
play the heel (v.)

(US) to act unpleasantly, to be mean or cruel.

K. Silber ‘Extreme Mars’ 21 Apr. at Space.com [Internet] His opponent, after all, was one of the most disliked individuals in the solar system. But somebody had to play the heel.