From the experts:
Corwin is an upstanding surname name that has been seen occasionally as a first in literature, but rarely in real life. But maybe with the recent acceptance of Darwin, that might change.
In the Water trilogy, Corwin appears as a teenage Merlin, and Prince Corwin is a main character in the the Chronicle of Amber series by Roger Zelazny.
Alternate definitions of the name are 'leather worker' and 'lives near a white enclosure or castle.' As a family name, it's associated with screen and radio writer Norman and Animal Planet host Jeff.