A beggar’s staff, with an iron hook at the end, to pluck clothes from an hedge, or any thing out of a casement. Filcher; the same as angler. Filching cove; a man thief. Filching mort; a woman thief.
Definition taken from The 1811 Dictionary of the Vulgar Tongue, originally by Francis Grose.
See also the definition in Nathan Bailey's 1736 dictionary of canting and thieving slang.
Figure Dancer * FileNathan Bailey's 1736 Dictionary of canting and thieving slang
John S. Farmer's collection of canting songs and slang rhymes