To work. The kiddy would not strap, so he went on the scamp: the lad would not work, and therefore robbed on the highway.
Definition taken from The 1811 Dictionary of the Vulgar Tongue, originally by Francis Grose.
Strangle Goose * StrapperNathan Bailey's 1736 Dictionary of canting and thieving slang
John S. Farmer's collection of canting songs and slang rhymes