This is what Donal O'Sullivan has to say in Carolan The Life Times and Music of an Irish Harper:

"...None of the above sources attributes this air to Carolan, but its style resembles his, and Hardiman states (p.lix) that it was composed by him for 'Captain O'Kane or O'Cahan, of a distinguished Antrim family, a sporting Irishman, well known in his day by the name of "Slasher O'Kane"'. I have been unable to find any further particulars about the Captain."

Perhaps Bonnie might know if there is any more recent information, otherwise you may be out of luck.

Mick