Mr. Thingstable; Mr. Constable: a ludicrous affectation of delicacy in avoiding the pronunciation of the first syllable in the title of that officer, which in sound has some similarity to an indecent monosyllable.
Definition taken from The 1811 Dictionary of the Vulgar Tongue, originally by Francis Grose.
Thimble * ThingumbobNathan Bailey's 1736 Dictionary of canting and thieving slang
John S. Farmer's collection of canting songs and slang rhymes