Wolfhounds

The word 'wolfhound' is relatively recent coinage, dating from the late eighteenth century (and therefore there is no Old English equivalent such as wulfhund). In Ireland, where this breed originated, a hound was known as a cú and a wolfhound as a cú faoil (where faoil means 'wolf'). The loyalty of a wolfhound was seen as a mark of nobility, and so cú came to be attached to lordly names (with the most famous example being the hero Cú Chulainn).

The idea that a wolfhound would reserve its loyalty for a deserving master has remarkable parallels to the tale of the hound Huan, who abandoned his cruel master Celegorm to aid Lúthien and Beren in their Quest for the Silmaril. There's a further parallel in Huan's name, which shares a derivation with Sindarin hû, 'dog, hound', from an ancient root khug-, said to mean 'bark'. The similarity of Sindarin hû to Irish cú is certainly notable, but whether Tolkien was influenced by the old Irish traditions surrounding these hounds is not recorded. If not, this would certainly be a remarkable coincidence.