Son of the traitorous Easterling chief Ulfang (S/157). This name seems to be Sindarin, and therefore was probably not his true name. It seems to be a combination of [N.] ul- “✱ugly” and the lenited form of [N.] gwarth “betrayer”.
Conceptual Development: This character was named N. Ulwar when he first appeared in Silmarillion drafts from the 1930s, later changed to N. Ulwarth (SM/320, LR/147). This second name appeared in The Etymologies as a combination of ᴹ√ULUG and N. gwarth, the source of the derivation given above (Ety/ÚLUG, WAR).
ul (stem “hideous, horrible”) + gwarth (“betrayer”)