Noldorin 

lhûn

adjective. blue

Noldorin [Ety/LUG²] Group: Eldamo. Published by

lhûn

adjective. (unknown meaning)

This word, which also appears on the map of Middle-earth in LotR, is glossed as "blue" in The Etymologies, but Tolkien later rejected this meaning (as luin was already used in that sense). He then proposed several explanations for it, including the possible adaptation of a Dwarvish name into Sindarin, but he apparently never reached a definitive solution.

Noldorin [Ety/370, VT/48:24-29] Group: SINDICT. Published by

lhûn

place name. Blue River

Noldorin [LRI/Lhûn; TI/124; TII/Lhûn] Group: Eldamo. Published by