Independent of the Scottish name, Iain appears in a few 12th century Irish Gaelic documents as a rare genitive (possessive) form of Eoin or Ioan, usually in place names and in religious contexts.t is treated as a separate name from Iain, which is now pronounced \EE-ahn\, \AHñ-@ee\, n \ñ-@or\. [ ay ] N ñ 13 the pronunciation Of the name-eoin eóin was re fashioned to match (the singular eun bird of which. the plural is eoin eòin