O Maccasa or O Macassey or O Maxey - Irish / Ua Macassey. A Heberian Eoghanacht Ui Fidgeinti Sept / Family branch who were the Chiefs of Corca Oiche / Ochae Sept who had their territory in Co. Limerick in the mid - north - west of the Munster Province. Ancestors: *90. Brion (Ui Brion) *89.Fiachu "Fidgennid" (Ui Fidgeinti) **88.Maine "Munchain," *87.Ailill "Fland Bec," *86.Fiacha "Mullethan" the 1st King of Southern Munster and 3rd King of Munster, *85.Eoghan "Mor" (Eoghanachta,) *84.Ailill "Oluimm" the 1st King of Munster.

Macarooney - Irish / Mheic Maol Ruanaidh. A Sept / Family branch, who had their territory in Co. Fermanagh in the south - west of the Ulster Province. Also see - Mac Arooney and Rooney.

Mack. Used as an abbreviation for any name beginning with Mac, such as Mac Enroe, in Co. Tyrone in Central Ulster or Mac Namara in Co. Clare in the north - west of the Munster Province.

Mackeady - Irish / Mheic Ceadaigh. An Irian Laeghis Ui Laoighis Sept / Family branch of the O More / Moore / Ui Mordha who had their territory in Co. Laois in the mid - north - west of Southern Leinster. Especially see - Mac Keady.

Mackeen. Used  for Mac Keane in Co. Clare in the north - west of the Munster Province.

O Macken - Irish / Ua Maicin / Ua Macain. A Sept / Family branch, who had their territory in Co. Down in the south - east of the Ulster Province.

O Macken - Irish / Ua Maicin / Ua Macain. An Ithian Corca Loigde Sept / Family branch, who had their territory in Co. Cork in Southern Munster. Ancestors: *36.Lewy / Lughaidh, *35.Ith (Ithians).

O Macken - Irish / Ua Maicin  / Ua Macain. A Sept / Family branch, who had their territory in Co. Mayo in the mid - west of the Connacht/ Province.

O Mackesy - Irish / Ua Macasa / Maghnus (Descended from *Manus) A Sept / Family branch, who had their territory in Co. Limerick in the mid - north west of the Munster Province. Some also changed to Mac Kessy and Mac Kissy, which see.

O Mackey - Irish / Mheic Macdha. A Sept / Family branch, who had their territory at Bally Mackey near Nenagh in the O Kennedy's Heberian kingdom of Ormond in Co. Tipperary in the north - east of the Munster Province and nearby in Co. Kilkenny in the south - west of Southern Leinster. Used as a synonym also for Mac Kee and Mac Kay, which see.

O Mackle. Originally Mackell - Irish / Ua Machail. A Sept / Family branch, who had their territory in Co. Armagh in the south - east of the Ulster Province but are now found on the western side of Loch Neagh. Some changed to Mac Kell or it was used as a synonym also for Mac Gill, which see, in Co. Down in the south - east of Ulster. Not connected to Mac Cahill.

Macklehatton. See - Mac Ilhatton.

Macklemoyle. See - Mac Ilmoyle.

Mackworth. See - Worth.

O Madden or O Madagan or O Maddison. A Heremonian Ui Cobhthaigh Ui Felim Dal Cuinn Colla da Crioch Sept / Family branch. Ancestors: *85.Murray / Muiredach "Colla da Crioch" / "Focrith" - of the Two Countries, *84.Eochy / Echu "Doimhlen," *83.Cairbre "Liffeachair" the 116th King of Tara / Ireland.

O Madden - Irish / Ui Madadhain - Madadhy / The hound. A Heremonian Ui Cobhthaigh UI Felim Dal Cuinn Ui Maine Sept / Family branch, who had their territory in the east of Co. Galway in Southern Connacht where they were Kings and Chiefs. They ruled there until the late Middle Ages and one of their Septs migrated to Co. Clare and Co. Limerick in the north - west of the Munster Province where they anglicized their name to O Madigan. One of their castles built in 1567 AD was at Brackloon, and another, Derryhivenny Castle, which was constructed in 1643 AD is now a ruin, and they were also Chiefs in Co. Offaly in the north - west of Southern Leinster. They continued to retain their territory even under the Norman de Burgo / Burke over - lordship and a branch also migrated to Co. Kildare in Central Southern Leinster. Ancestors: *86.Maine "Mor" (Ui Maine), *85.Murray / Muiredach “Tireach” the 122nd King of Tara / Ireland, *84.Fiacha “Sraibhtine” the 120th King of Tara / Ireland, *83.Cairbre "Liffeachair" the 116th King of Tara / Ireland, *82.Cormac mac Airt  the 115th King of Tara / Ireland, *81.Art "Eanfhear" the 112th King of Tara / Ireland, *80.Conn of the Hundred Battles the 110th King of Tara / Ireland (Dal Cuinn).