Green’s Dictionary of Slang

dominicker n.

also dominecker
[SE dominicker, the Dominique fowl or any other chicken with mottled or barred plumage. The dominicker rooster was believed always to back down when challenged by another rooster]
(W.I.)

1. a coward.

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[US]R. Bradford This Side of Jordan 254: Come on, you dominecker.

2. a person of mixed race, esp. of black, Indian and white ancestry.

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Federal Writers Project Florida 445: In adjacent back country live ‘Dominickers,’ part Negro and part white, whose history goesd back to the early 1860s [...] The name originated [...] when a white in suing for divorce described his wife as ‘black and white, like an old Dominicker chicken.’ .