Cù Sìth / Cú Sídhe

The name as recorded in the sources combines two Gaelic elements attested in the cited references: cù / cú, the common Gaelic word for 'hound', and sìth / sídhe, an element associated in Gaelic vocabulary with the Otherworld or fairy realm. The brief encyclopedic references identify the creature as a named class of otherworldly hound in Irish and Scottish tradition and place it among the family of Celtic otherworld hounds by explicit comparison to the Welsh Cŵn Annwn. The supplied sources do not provide a narrative origin myth, genealogy, or stories detailing the creature's first emergence; they only situate the name and concept within regional folklore.

The provided sources characterize the cù-sìth / cú sídhe simply as a 'mythical hound' and do not supply detailed physical descriptions. Beyond the classification as a supernatural canine, no documentary details about size, color, number of heads, or other distinguishing corporeal traits are given in the cited material. Any more specific physical description would require sources beyond those provided.

The available references do not enumerate specific powers, abilities, or habitual behaviors for the cù-sìth / cú sídhe. The sole behavioral inference in the sources is comparative: the creature 'bears some resemblance to the Welsh Cŵn Annwn,' a class of otherworld hounds in a neighboring Celtic tradition. That comparison indicates a conceptual affinity to otherworld-associated canines but does not authorize the attribution of particular abilities to the cù-sìth in these sources themselves. Consequently, no discrete abilities are documented here.