Eason, Essie, Eassie
Eason, Essie, Eassie—These three names are the anglicised forms of a McIntosh sept called McAy, but have no connection with MacKay, though written the same way in Gaelic, Mac Aoidh. Ayson is a form.
Alphabetical Index of Anglicised Surnames in Ireland
See also Woulfe’s Irish Names and Surnames
… and O'Hart's Irish Pedigrees