In Irish, "cathair mhór" means simply "great stone fort", and the name alone suggests something substantial once stood or still stands here, a monument substantial enough to earn that distinction from the people who named the land around it. Stone forts of this type, sometimes called cashels, are circular enclosures built from dry-stone walling, used in early medieval Ireland as farmsteads or places of refuge, and the "mór" suffix was not applied lightly.

Brodullagh, the townland in which Cahermore sits, lies in the west of Mayo, a county that preserves an unusually dense record of early settlement in its landscape. The region was inhabited continuously from the Neolithic period onward, and the survival of place-names compounding "cathair" with qualifiers like "mhór" often points to enclosures that were once prominent local landmarks, even where the physical remains have since been robbed for field walls or reduced to a grass-covered ring. Without more detailed documentation to draw on, the precise condition of any surviving structure here remains unclear, but the name itself is the oldest form of record, one that outlasts stone.