My name's Allen, and I'm a prodigal Kingman who's relocated to Alaska.
To clear up a small bit of your confusion about the British ancestry of the American Kingmans, my research confirmed that we are all descendants of Henry Kingman who came to the Massachusets colony in 1635 along with his wife, children and a servant.(I determined this from study of original ships' passanger lists.Don't recall the name of the ship, but it wasn't hard to find.)He departed England from Weymouth, which is a port, but he lived in Frome, Somerset.I was interested to read that someone had found a father or grandfather of Henry named William Kingman who was also from Frome.
I haven't found any references at all to the Kingman name anywhere in England prior to Henry, so it wouldn't surprise me at all that previous descendants came from Wales.But there are two other factors to consider.First, spelling of names back then wasn't particularly standardized.While there are no earlier English references to Kingman, there are many references to "Kingsman", a name that has origins in the 13th or 14th centuries.Kingman could simply be a variant of Kingsman.Second, one cannot forget that the religious and political strife of the 16th century resulted in the destruction of many (or most) churches and their records.These church records were the only real records of births, deaths, marriages, etc., in the era, so it's very likely that there isn't going to be any written record of Henry Kingman's ancestors in Somerset.