Sindarin 

lach

noun. (leaping) flame

An element meaning “flame” appearing in many names. Christopher Tolkien gave its form as lhach “leaping flame” in the Silmarillion appendix (SA/lhach), but given Lachend “Flame-eyed” (WJ/384) and lacho calad! “flame light!” (UT/65), I think ✱lach is the likelier Sindarin form, which is the form also suggested by HSD (HSD).

Conceptual Development: ᴱN. lhacha “flame” appeared in Early Noldorin Word-lists of the 1920s (PE13/148).

Sindarin [SA/lhach; WJ/384] Group: Eldamo. Published by