From Tolkien Gateway
This article or section needs more/new/more-detailed sources to conform to a higher standard and to provide proof for claims made.
NIMIR is a Mannish (perhaps specifically Adûnaic) root base related to the Elves.
Adûnaic: Nimîr, Nimriyê, Nimrûn Nimruzîr
It's possible that it derived from the word Nómin, a Taliska name for the Elves.