Scottish, Anglicized form of the Gaelic name Eóghan, "born of [or under] the yew". [But see also under Ewan.]
In old documents in Latin, Eugenius is used for Euan/Ewan/Ewen as well as for Eugene, which we have therefore classified as a Lesser Synonym. Care must be taken when searching to allow for Latin case endings.
There appears to be some connection with Evan which may also be an Anglicized form of the Gaelic name Eóghan.