Originally means something before was changed.
Denn is a short form of Dennis, which was and is a first name in England- probably inspired by St Denis and St. Dionysius
Occupational form: From "Wefan", meaning to weave. Geographical form: From Weaver Hall in the county of Cheshire
It means "the lady" or "the mistress of the house"
Probably son of Wilhelm, prob. from German root & originated in the UK after the Norman conquest