P W Joyce in English as we speak it (1910) gives:

Leprachaun; A sort of fairy, called by several names in different parts of Ireland: - luricaun, cluricaun, lurragadaun, loghryman, luprachaun. This last is the nearest to the Gaelic original, all the preceding anglicised forms being derived from it. Luprachaun itself is derived by metathesis from Irish luchorpán, from lu, little and corpán, the diminutive of corp, a body...."


While Joyce is an old source at this stage, he is probably reliable enough.


Regards