Green’s Dictionary of Slang

a beggar who fakes dumbness in order to gain alms.

1608		Dekker Belman of London D2: Equall to the Crancke in dissembling is the Dummerar, for as the other takes vpon him to haue the falling sicknesse, so this counterfeits Dumbnes; but let him be whipped well, and his tongue (which he doubles in his mouth, and so makes a horred and strange noise in stead of speech), will walke as fast as his handes doe, when he comes where any booty is.
1621		R. Burton Anatomy of Melancholy (1850) 216: We have dummerers, Abraham men, &c. And that which is the extent of misery, it enforceth them through anguish and wearisomeness of their lives, to make away themselves; they had rather be hanged, drowned, &c., than to live without means.
1707		J. Shirley Triumph of Wit 183: The Dummerers are such as make a horrible Noise, attended with many antick Postures, and frequently signify, not only by Signs, which to every one are not intelligible, but by a forged Writing, that their Tongues were cut out in the Turkish Slavery.
1749		B.M. Carew ‘The Oath of the Canting Crew’ in Farmer Musa Pedestris (1896) 51: No dummerar, or romany; / No member of the family.
1754		Scoundrel’s Dict.
1834		(con. 1737–9) W.H. Ainsworth Rookwood (1857) 162: The dummerar, whose tongue had been cut out by the Algerines, suddenly found the use of it, and made the welkin ring with his shouts.
1867		(con. 1600s) M. Lemon Leyton Hall I 237: Tabitha and her young master soon reached Bread-street after this escape from the dummerer (as he was called in Pedlar’s French).
1925		D. Hammett ‘Dead Yellow Women’ Story Omnibus (1966) 155: Uhl was a dummerer who had lost his store [...] Any day on which his sad face, his package of pins, and his I am deaf and dumb sign didn’t take twenty dollars out of the office buildings [...] was a rotten day.