Several early sources use "Iye" in Mackay pedigree charts. "The Book of Mackay", section IV, The Strathy Mackays, by Norman Macleod pub Edinburgh 1906 uses the forename "Iye". Montcrieff and Hicks in "The Highland Clans" refer to the transliteration with Gaelic, Latin, and English in the use of "Y". Mackay in Gaelic is "Mac Aodh", son of Aodh. In very early times, the name was spelled "Aed",later "Aedh". The old Scots chroniclers sometimes wrote the name as "Eth", "Ed", or "Heth". As late as the 17th century, it was just "Y" Mackay for "Aodh mac Aoidh". During the 16th century, the name was often Anglicised as "Hugh". By rights there should be no "k" in Mackay, but it has been used that way for centuries. Hope this helps a pinch.