I agree that the roman influence through occupation has merit. Whether it was used as a first or last name is not consequential. The reference to Sir
Gawain in the
Mallory's poem (alleged-but most likely) may have less to do with the meaning of the name. Both Sir
John Gawen and
Mallory both served in British parliament around the same time. It may be that
Mallory wrote his stories (while in jail) and incorporated known people into his characters much like Shakespeare or other playful writers at the time. The actual Middle English spelling in the earliest manuscript was Gawen. Gawyn and Gawan and all kinds of variations were used as first names as
Gavin is today. An alternate meaning is "son of a smith". The Germanic pronunciation of Gawen is
Gavin. That's much closer to the latin form Gavinus, which indead means "white hawk" or simply a white bird of prey. At the time the name emerged in medieval England white Boussards were plentiful. They are now extinct.