The word ‘wraig’ is mutated from ‘gwraig’, which means woman or wife.
The cairn to the north is a ring cairn, and it’s labelled Carn Saith-Wraig on the old Ordnance Survey maps. The cairn to the south is a badly damaged round cairn, and it is unlabelled on the maps. On the National Monument Record it carries name Saith-Wraig, Round Cairn but I suspect this is by association with its neighbour.
The reason I mention all this is that you can’t have the name ‘Carn Saith-Wraig’ for more than one cairn. The word ‘carn’ means cairn, not cairns. The plural is ‘Carneddau’, so if both sites shared the name they would collectively be called ‘Carneddau Saith-Wraig’... I think.