Green’s Dictionary of Slang

prag n.

[var. on prig n.1 (2)]

(UK Und.) a thief.

[UK]Greene Disputation Betweene a Hee and a Shee Conny-Catcher (1923) 11: The cunningest Foyst, Nip, Lift, Pragge, or whatsoever that lives at this day.