Most accounts say that Unwin is a Saxon name also used as a first name right up to the 1300s. It might be derived from the Old English "unwine" meaning "unfriend" or "enemy"; "hune wen" meanign "little friend" or Hun Wen, son of Vandal.
It would appear that the name originated in East Anglia: In the Domesday Book, there is a Hunuuinus in Cambridgeshire and in 1166 a Hunwine de Batha, also called also Vnwine, in Norfolk. The surname, either Hunwin(e) or Unwin, is found in Cambridgeshire, Suffolk, Essex, and Norfolk in the 13th and 14th centuries..
There are Saxon folk histories which mention Unwen "son born beyond hope", which would have been told (and, most probably, old then) in King Alfred's time. Versions also appear in the 14th Century Fasciculus Morum and the alliterative Morte Arthure, in which Unwyn, king of Thetford, fights in single combat agains Attalus.