E. Cobham Brewer 18101897. Dictionary of Phrase and Fable. 1898.
Gander (g hard).
Whats sauce for the goose is sauce for the gander. Both must be treated exactly alike. Applesauce is just as good for one as the other. (Anglo-Saxon gós, related to gons and gans. The d and r of gan-a are merely euphonic; the a being the masculine suffix. Thus han-a was the masculine of hen. Latin, anser.)