E. Cobham Brewer 1810–1897. Dictionary of Phrase and Fable. 1898.
Blue Hen.
Captain Caldwell used to say that no cock could be truly game whose mother was not a blue hen. As Caldwell commanded the 1st Delaware regiment in the war, the State of Delaware was nicknamed Blue Hen.
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Your mother was a blue hen, no doubt. A reproof given to a braggart. (See above.)
