(A) is the Anglo-Saxon word wencle, a child. It is now chiefly used derogatorily, and the word wenching is quite offensive. In the Midland counties, when a peasant addresses his wife as “my wench,” he expresses endearment.
Wench, like girl, was at one time applied to either sex, Chaucer has “yonge-girls” for youngsters of both sexes. We find the phrase “knave-girl” used for boys; and Isaac, in the Ormulum, is called a wench or wenchel. Similarly, “maid” is applied to both sexes, hence the compound moeden-foemne, a female child or maiden
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894