Tolkien experimented with a variety of similar terms the Sindar appeared on the back page of Notes on Names (NN) from 1957, including egl, egel, egel, egleðel and eglon (PE17/140-142). These also several atypical plural forms, resulting from developments from ✶eklō/etlō via syllabification of -l > -ol:
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igil: The -l vocalizes to -il instead of -ol. Before the vocalization took place, the plural mutation was carried out to produce igl, which explains, why the resulting form is igil instead of egil, which would be usual for e in non-final syllables.
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igli: This form is rather unusual for a Sindarin word, as final vowels usually vanish, but the note also includes what seems to be a direct reference to this rule “?ḷ́ < li, ṛ́ < ri” (PE17/142).
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iglin: A plural with the suffix -in. This is comparable to the plural form Nauglin of naugl, naugol, which developed similarly. Interestingly, the first e mutates to i, which is unusual for non-final e
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eglir: The suffix -ir is rather unusual outside of Notes on Names, but occurs there for various other forms: Thind → Thinnir, Dúnel → Dúnellir, Noll → Nellir. Here, unlike in iglin the first e remains unchanged.
Tolkien eventually replaced all these variations with S. Eglan (WJ/365), whose (class) plural form Eglath was used in The Silmarillion as published (S/58).
masc. n. a name of the Noldor given by the Sindar. probably a masculine form of egel.