(plural chickens ). It is quite a mistake to suppose “chickens” to be a double plural. The Anglo-Saxon is cicen, plural cicen-u. We have a few plural forms in-en, as ox-en, brack-en, children, brethren, hosen, and eyen; but of these children and brethren are not the most ancient forms. “Chick” is a mere contraction of chicken.
The old plural forms of “child” are child-r-e, dialectic child-er; children is a later form. The old plural forms of “brother” are brothru, brothre, brethre; later forms are brethren and brothres (now brothers).
Children and chicken must always be pickin'. Are always hungry and ready to eat food. To count your chickens ere they are hatched (Hudibras). To anticipate profits before they come. One of Æsop's fables describes a market woman saying she would get so much for her eggs, with the money she would buy a goose; the goose in time would bring her so much, with which she would buy a cow, and so on; but in her excitement she kicked over her basket, and all her eggs were broken. The Latins said, “Don't sing your song of triumph before you have won the victory” (ante victoriam canere triumphum). “Don't crow till you are out of the wood” has a similar meaning. (See page 36, col. 2, Alnaschar's Dream)
Curses like chickens come home to roost. (See under Curses)
Mother Carey's chickens. (See Mother Carey)
She's no chicken. Not young. The young child as well as the young fowl is called a chicken or chick.
Chicken of St. Nicholas (The). So the Piedmontese call the ladybird, or little red beetle with spots of black, called by the Russians “God's little cow,” and by the Germans, “God's little horse” sent as a messenger of love.
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894