says E. Adams (English Language), properly means a bar?maid; ?- ster? is the Anglo-Saxon feminine suffix ?estre, which remains in spin-ster (a female spinner).
This is only a half-truth. After the thirteenth century, the suffix?ster was used for an agent of either sex. We have barrister, gamester, punster, etc., and Wickliffe uses songster for a male singer (See Dr. Morris Historic Outlines, p. 89.)