The Elves who refused to journey to Aman, an agental formation of the ancient verb ava- “to refuse” with the common agental suffix -r(o) (VT47/13, WJ/371). This name most frequently appeared in its plural form Avari referring to this entire people (S/52).
Conceptual Development: The name ᴹQ. Avar(o) first appeared in plural form * in Tolkien’s linguistic notes from the 1930s with the gloss “The Departing”, and referred to those elves who left Middle-earth, whereas those who remained were referred to by the earlier name the ᴹQ. Lembi “Lingerers” (LR/169-170). Tolkien soon revised this name to refer to the Elves who remained behind, effectively replacing the term Lembi (LR/200). This name appeared in The Etymologies* with essentially the same derivation as given above (Ety/AB).
avar noun "recusant, one who refuses to act as advised or commanded"; pl. Avari Elves that refused to join in the westward march to Aman (WJ:371, singular Avar in WJ:377 and VT47:13, 24).The Etymologies gives Avar or Avaro, pl. Avari "Elves who never left Middle-earth or began the march" (AB/ABAR)