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| Grealis | fairly rare: Mayo. Ir. Mag Riallais. See Grealish. |
| Grealish | Quite numerous: Galway. Ir. Mag Riallais, which is a corruption of the Ulster name Mac Niallais. SI & SGG. |
| Mag Riallghuis | Grealish: líon beag: Gaillimh. Claochlú ar an sloinne Ultach Mac Niallghuis. Préamh: Niall + gus (fuinneamh). |
Parishes where a Grealis and a second surname married each other.