O Meighan - Mernagh 

O Meighan. Used as a variant for O Meehan, O Mehegan and O Meekin, which see.

Melamby. See - Mullanphy.

Melay. See - Millea.

Meldon. Used as a synonym for Muldoon, which see.

Meldrum. Scottish locative origins. They have been in the Ulster  Province and Northern Connacht since the Confiscation of the 3,500,000 acres of the Heremonian Ui Cobhthaigh Dal Cuinn "Northern" Ui Niaill territories there and the Foreign non - Catholic Plantations there in the early 17th Century AD.

O Melia See - O Malley.

O Melican - Irish / Ua Maoileachain. Actually O Molohan / Ua Maolachain, which see. They had their territory in the west of Co. Clare in the north - west of Thomond / Tuaiscert Mhumhain / Northern Munster.

Mellott. See - Millett.

Mellin. Used as a variant for Malinn, which see.

Mellis. See - Malise.

O Melly - Irish / Ua Meallaigh - meall - pleasant. A Sept / Family branch, who had their territory in Northern Connacht and nearby in Co. Donegal in the north - west of the Ulster Province. Not connected to O Malley.

Melvin. See Blehin and Mulvin.

Menaght. Used for Mac Naughten, which see, in Co. Down in the south - east of the Ulster Province.

Menarry or Mac Nary or Mac Neary - Irish / Mheic Naradhaigh - nardach / modest. A Sept / Family branch, who had their territory in the Heremonian Ui Cobhthaigh Dal Cuinn 3 Colla kingdom of Orghialla / Airghialla / Oriel in Southern Ulster and nearby in Co. Louth in the north - east of Northern Leinster.

Mac Menim or Mac Menin. Used for Mac Menamin, which see, in Co. Tyrone in Central Ulster.

Menogher. Used for Mac Nogher, which see.

O Menton or O Mentin or O Mentane - Irish / Ua Manntain. A Sept / Family branch, who had their territory in the Munster Province. See also - Manton.

Meran. Used as a variant for Marron, which see.

Mercer / le mercier (the merchant) French occupational name. They were in the Leinster Province in Medieval Times and later in Co. Antrim and nearby in Co. Down in the east of the Ulster Province.

Mercier. Used as a variant for Mercer, which see, in Co. Offaly in the north - west of Southern Leinster and other Northern Leinster regions.

Meredith. (magnificent) Welsh origins.They were in Ireland in the 16th Century AD.

Mergagh - Irish / Meirgeach (freckled). One of the 7 names used to anglicize their name by the Irish O Hingerdells, which see. A Sept / Family branch, who had their territory in Co. Cork in Desmond / Des Mhumhain / Southern Munster.

Mergin. Used as variant for Bergin, which see.

O Merlehan - Irish / Ua Meirleachain (meirleach / rebel). A Sept / Family branch, who had their territory in Co. Westmeath in the south - west of Northern Leinster.

Mernagh - Irish (mearnach - deft). A Sept / Family branch, who had their territory in Co. Wexford in the south - east of Southern Leinster. May have been a sub - Sept of the Heremonian Ui Laoghaire Ui Cheinnselaig Mac Murrough - Kavanagh Septs, which see.