Nan was a Giant, mentioned only in The Book of Lost Tales 2, for whom the Nauglafring (the early name of the Necklace of the Dwarves) was made. He and another Giant Gilim are not told of in The Silmarillion.
Nan is told in The Tale of Tinúviel to have owned a particularly long sword, named Glend.
References
- The History of Middle-earth, Vol. II: The Book of Lost Tales 2, chapter 1, "The Tale of Tinúviel"