Green’s Dictionary of Slang

heel n.

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

1. [1900s–30s] (US Und.) constr. with the, ‘The racket of stealing by sneaking’ (Sutherland, The Professional Thief, 1937).

2. [20C+] (orig. US) a petty criminal.

3. [1910s+] (orig. US) a general derog., esp. a dishonest, untrustworthy person, esp. one who treats women badly.

4. [1920s+] (US Und.) an informer.

In phrases

on the heel [1910s–40s] (US Und.)

1. working as a criminal.

2. till-tapping.

play the heel (v.)

[1910s+] (US) to act unpleasantly, to be mean or cruel.