My dictionary (
Leslie Dunkling 1983) says:
"Modern use is due entirely to
Marlon Brando..
[his] family is said to be of French origin..
Marlon is not a French first name, and the closest one can get to it in a French context is the family name
Marlin, indicating an ancestor whose name was
Merlin."
Presumably the French
Merlin surname would have been derived like
Andy said, since the English male first name
Merlin has an unrelated etymology from approximated Welsh.. however my book suggests the feminine English first name
Merlin is for the bird.. whoa off topic.
- chazda