The name Oisin is a boy's name of Irish origin meaning "little deer". Oisin and is often added to lists like Mythology Boy Names and discussed in our forums with posts like "Change two letters (5 names)".
From the experts:
Oisin, one of the most popular Irish baby names in its native land, though largely unknown in the US, is also spelled as the phonetic Osheen. The original Oisin was the mythological son of Finn McCool and Sadb, the goddess who was changed into a deer. A legendary war hero and poet, Oisin had a name that is also reminiscent in sound of the ocean. Pronounced correctly, this name has an attractive sheen.
Ossian is another version, reflected in the eighteenth century Ossianic poems of James Macpherson, which transformed him into a Scottish hero and also popularized the names Oscar, Fingal, Selma and Malvina.