Green’s Dictionary of Slang

(UK Und.) a thief-taker.

1725		New Canting Dict.
1728		T. Walker The Quaker’s Opera II i: And when we come unto the Whit, / Our Darbies to behold [...] we bouze the Water Cold. / But as I’ve liv’d to come out again, / If the merry Old Roger I meet, / I’ll tout his Muns, and I’ll snable his Poll / As he Pikes along the Street.
1737, 1759, 1760, 1776		Bailey Universal Etym. Eng. Dict.