Green’s Dictionary of Slang

the profession of highway robbery.

1751		Fielding Amelia (1926) I 16: I thought by your look you had been a clever fellow, and upon the snaffling lay.
1903		Cincinnati Enquirer (OH) 11 July 2/4: It is more than a century since in England the profession of a highwayman, the ‘snaffling lay’ [...] was wiped out.