Green’s Dictionary of Slang

bustrap n.

[buzz n. (3a) + SE trap]

a thief-catcher.

1753
1760177017801790
1799
[UK]J. Poulter Discoveries (1774) 42: The Bustrap johns me; the Thief-catcher knows me.
[UK]Whole Art of Thieving .
[UK] ‘The Cant Lang. of Thieves’ Monthly Mag. 7 Jan.