Green’s Dictionary of Slang

(UK Und.) safe.

1719		A. Smith Lives of Most Notorious Highway-men, etc. (1926) 207: [...] There’s a cull knows us, if we don’t picque he’ll bone us, i.e., that fellow sees us, if we don’t scout off, he’ll apprehend us. Ding him, i.e., knock him down. Then we’ll picque, ’tis all boman, i.e., We’ll be gone, all is well, the coast is clear.
1725		New Canting Dict. n.p.: Then we’ll pike, ’tis all Bowman; We’ll be gone, all’s well, the Coast is clear.
1737, 1759, 1760, 1776		Bailey Universal Etym. Eng. Dict. [as cit. 1725].
1786		Whole Art of Thieving n.p.: All’s bowman all is safe.