Green’s Dictionary of Slang

1. a dominant, aggressive and esp. short-tempered person, esp. a woman.

1818

A.N. Royall Letters from Alabama 18 Jan. 146: He told one of our party he was ‘one of the blue hen’s chickens’.

2. a resident of the state of Delaware.

1840		Niles’ Register 9 May 154/3: In the revolutionary war [...] Captain Caldwell [of Delaware] had a company called by the rest ‘Caldwell’s game cocks’, and the regiment after a time in Carolina was nicknamed from this, ‘the blue hen’s chickens’ and the ‘blue chickens’. [...] But after they had been distinguished in the south the name of the Blue Hen was applied to the state [DAE].
1853		N.Y. Clipper 9 July 6/4: On the right hand will be observed a fire-cracker, surrounded by three chickens of the blue hen, who are vainly endeavoring to set it off.
1856		Congressional Globe 12 July 1056: Yes, sir, the blue hen’s chickens, the descendants of the cocks which crowed and fought so bravely in the times which tried men’s souls.
1864		Congressional Globe June 2968/2: I remember the early history of the Blue Hen’s Chickens and it is a proud one [DA].

3. (US) a spirited, plucky person, a good fighter.

1909

J. Ware Passing Eng. of the Victorian Era 37/2: Blue Hen’s Chick (Devonshire). A clever soul, e.g., ‘You’re a blue hen’s chick hatched behind the door’ — said satirically.

4. an important person or one who poses as such.

1946		PADS VI 6: Blue hen’s chickens [...] local aristocracy.
1951		AS XXVI 196: Blue hen’s chicks [...] ‘high-toned’ people who ‘think they are just a little better than someone else’.
1970		in DARE.