Oisín

It is pronounced Ush-een. Oisín left the Fianna to go to Tír na nÓg (land of the young) where one would never grow old. A woman (forgot her name) brought him there. After, what he thought was only a few weeks he asked to go back to his own land to see his people. The woman allowed him to, but warned him not to get off his horse. Long story short, it was about 300 years later and all his friends were dead. He fell off the horse and became very old. He supposedly told his story to St. Patrick (patron saint of Ireland) before he died.