What Does “Magh” Mean in Irish Placenames?

Towns and cities with Magh

Armagh · Ard Mhacha · County Armagh
'Macha's height' — the goddess of the Ulster sagas
Omagh · An Ómaigh · County Tyrone
'the virgin plain' or 'the seat'
Maghera · Machaire Rátha · County Derry / Londonderry
'plain of the ringfort'; Joyce agrees (Machaire-ratha, 'the plain of the fort') and records an older name, Rath-murbhuilg, 'the rath of the sea-inlet'
Maynooth · Maigh Nuad · County Kildare
Plain of Nuadha, from Maigh Nuadhat; the article takes Nuadha as one of the gods of the ancient Irish, while Joyce, following O'Donovan, takes the name from Nuadhat, a king of Leinster

Quick answers

What does Magh mean in Irish place names?

Plain: it is the Irish magh / maigh. It is written Magh, Moy, Maw, May in English spellings of Irish names.

How is Magh spelled in Irish?

magh / maigh. English spellings of the same word include Magh, Moy, Maw, May, because the names were written down by ear.

Which towns have Magh in their name?

Armagh (Ard Mhacha), Omagh (An Ómaigh), Maghera (Machaire Rátha), Maynooth (Maigh Nuad).