From Tolkien Gateway

Oikeroi was a cat according to the early version of the legendarium in The Book of Lost Tales.


He was a thane of Tevildo, described as warlike and fierce, but he was killed by Huan.[1] Huan gave the coat of Oikeroi to Lúthien, who used it to disguise Beren on their quest to retrieve a Silmaril from Melko. Oikeroi had previously spent a good deal of time about the hall of Melko, allowing Beren to pass unnoticed.[2]

In later writings, Beren was disguised in the coat of the great wolf Draugluin, rather than the coat of Oikeroi.[3]