To play on any instrument sttfnged with wire. A thrummer of wire; a player on the spinet, harpsichord, of guitar.
Definition taken from The 1811 Dictionary of the Vulgar Tongue, originally by Francis Grose.
Throttle * ThrumsNathan Bailey's 1736 Dictionary of canting and thieving slang
John S. Farmer's collection of canting songs and slang rhymes