One of the twelve companions of Barahir (S/155). His name seems to be the noun dagnir “slayer” used as a name.
Conceptual Development: In Silmarillion drafts from the 1930s, this character was first named N. Dengar, soon changed to N. Dagnir (SM/319).
A word for “slayer” (PE17/97), a noun form of dag- “to slay” with the agental suffix -nir, appearing in the (somewhat loosely translated) phrase: Túrin Turambar Dagnir Glaurunga “Túrin Turambar, Glaurung’s Bane” (S/226). I would use this word as “bane” only in the sense of “one who has killed” or “one who will kill”.