One mid-nineteenth-century author writes:

‘The great cavern at Tanyrogo’ was formerly believed to be ‘enchanted’ and to contain hidden treasures, guarded by a great dog of a supernatural species, kept here by the Three Fairy Sisters whose footmarks were always to be seen in the mud of a small lodgement of water within the mouth of the cavern (Williams 1860, 224).’

The caves are also mentioned in the Welsh tale of fairies: the Fairy Password.

Note that Tan yr Ogo is the name of a nearby farm-house: note the Tan-yr-ogof Farm