The Women's Lib underground biweekly It Ain't Me, Babe, put out by six young women who are all cartoonists and all mad at male cartoonists who draw women as nags, vultures, or dumbies. 1970, Vogue, volume 156, page 144:
1910, John McElroy (1846-1929), Si Klegg
"Ketch what? Great grief, ketch what?" groaned Si. "They've already ketched everything in this mortal world that was ketchable. Now what are they goin' to ketch?"
"Why, the smallpox, you dumby," said the Surgeon irritably. "Don't you know that we are terribly afraid of a visitation of smallpox to the army? […]
(alt-of, archaic) Archaic form of dummy (“hand shown to be played from by another player”).