Ilkorin was a language (and to a lesser extent, a populace) Tolkien wrote in the earliest versions of his Legendarium. It was the language of those who were not of Kôr. It was, as such, replaced by Sindarin and Avarin. In The Etymologies, some names (for example, the rivernames of Ossiriand) are said to be of Ilkorin origin. However, in later notes1, some of those names were renamed or given another etymology. In this same phase, North Sindarin was conceived, and it replaced many of the linguitic features.