Green’s Dictionary of Slang

beck n.1

[abbr. harman n.]

(UK Und.) a constable.

[UK]B.E. Dict. Canting Crew n.p.: Beck, a Beedle.
[UK]Grose Classical Dict. of the Vulgar Tongue.
[UK]Lex. Balatronicum.
[UK]Egan Grose’s Classical Dict. of the Vulgar Tongue.
[UK]Flash Dict. in Sinks of London Laid Open.