Lembi noun "Elves remaining behind" = Telerin Ilkorins (LEB/LEM, PE17:143). Sg. #Lembë. Also called Úamanyar.
Quenya
lembi
collective name. Lingerers
Lembi
elves remaining behind
úamanyar
those not of aman
Úamanyar noun "those not of Aman" (sg. Úamanya, PE17:143), Elves who did not reach the Blessed Realm (but did leave Cuiviénen with the intention of going there) = Heceldi _(WJ:371). Also Úmanyar and fuller Úmaneldi. (WJ:373)_. Also called Lembi, q.v.
úmanyar
those not of aman
Úmanyar pl. noun "those not of Aman", Eldar that did not reach Aman, sc. Sindar and Nandor _(SA:mān). _Sg. #Úmanya.Also Úamanyar.
An early name for the Elves who “stayed behind” in Middle-earth (MR/169, PM/61). It is most likely a plural noun derived from the adjective [ᴹQ.] lemba “left behind” (Ety/LEB).
Conceptual Development: This name was used for various purposes in Tolkien’s writing.
When the term first appeared in notes from the 1930s, ᴹQ. Lembi was used for the Elves that refused to march to Valinor, as opposed to the Eldar (LR/169), but later that group was called the Avari “The Refusers” (LR/170, WJ/371).
In Silmarillion drafts from the early 1950s, the term Lembi (also in a revised form Lemberi) was used for the Elves who were left behind in Beleriand (MR/169, PM/30), but this term was changed to the Ecelli “The Forsaken” (MR/169-170), later still to the Heceldi (WJ/365) or the Sindar (WJ/175).
Even later, the term Úmanyar “Those Not of Aman” was introduced to include both the Elves who refused to march and the Elves who were left behind (MR/170, WJ/365).
Since all the uses of Lembi were replaced by other terms, it seems likely that the word was no longer valid in Tolkien’s later writings.
In addition to the form Lembi, this name sometimes appeared as Lemberi (MR/169; PE18/24) and in one place as Lembar (PE18/24).