Early 20th century coinage, apparently invented by Oscar Wilde, who used it for the main character in The Portrait of Dorian Gray (1891)
He probably took it from Late Latin Dorianus, from Greek Dorieus, a member of the Greek-speaking people who settled in the Peloponnese in pre-classical times. Dorian would thus be a male form of Doris. 
Dorian Gray, invented by Oscar Wilde, is a dissolute rake who retains unblemished youthful good looks; in the attic of his home is a portrait which does his ageing for him, gradually acquiring all the outward marks of his depravity. 
|Female ♀||Male ♂|
|#: count of main first name only|
|&: count of both main and additional first names|
| Name counts are approximate as statistics normally is not published
for names given to less than 3 or 5 persons per country.