Origin

The name Oisin probably originated in the myth of Tír na nÓg

Tír na nÓg

Tír na nÓg is the most popular of the Otherworlds in Irish mythology. It is perhaps best known from the story of Oisín, one of the few mortals who lived there, who was said to have been brought there by Niamh of the Golden Hair. It was where the Tuatha Dé Danann settled when they left Ireland's...

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Oisin was the son of Fionn mac Cumhaill

Fionn mac Cumhaill

Fionn mac Cumhaill , known in English as Finn McCool, was a mythical hunter-warrior of Irish mythology, occurring also in the mythologies of Scotland and the Isle of Man...

 and was brand to the land of youth by beautiful Niamh.

McPherson and Ossian

James Macpherson

James Macpherson

James Macpherson was a Scottish writer, poet, literary collector and politician, known as the "translator" of the Ossian cycle of poems.-Early life:...

claimed to have found old poems from Ossian (or Oisin).
While there is doubt if he had genuinely found ancient texts directly from Oisin, the tales found in the poems were popular and common in the oral tradition of the Scottish Highlanders.

Variants and Pronunciations

Oisín. (uh-SHEEN)
Also pronounced "Osh-EEN" in Ulster.

Ossian. (oss-e-an)