Green’s Dictionary of Slang

(UK Und.) clever, capable.

1846

Swell’s Night Guide 51: The nummy pet gammoned scrapping, stalled a prop in the mug, propped in return, and floored Fuzzle, who gammoned a downer [...] and frisked him rumbo. [Ibid.] 75: No one dares dispute the ability of the boshman; cos he’s the pet of the motts, and a numming slogger.