The fairy dog of Scottish Gaelic folklore. It is said to be
as large as a two-year-old stirk, a dark green color, with ears of deep green. It is of lighter color towards the feet. In some cases it has a long tail rolled up in a coil on its back, but others have the tail flat and plated like the straw rug of a pack-saddle. Its paws are the size of a man's hand.
The cù sìth was usually kept tied as a watch dog in the brugh, the fairy dwelling, but at times accompanied the women on their expeditions. It also wandered about alone, making its lair in clefts of the rocks. The dog moved silently, although some said that it made a noise like a horse galloping. Its bark was described as a rude clamor, or like that of another dog, only louder. There was a considerable interval between each bark, and at the third (it only barks thrice) the hearer was overtaken and killed, unless he had found a place of safety.
- Campbell, J.G. (1900). Superstitions of the Highlands and Islands of Scotland. Glascow: James MacLehose and Sons, pp. 30-32.