Stated in the Etymologies to be derived from a stem ÉLED (LR:356), defined as "Star-folk"; Tolkien points out that Doriathrin and Danian used a "transposed" form, clearly referring to the sounds L and D changing place. In Etym the development is apparently meant to be eledâ (this primitive form is explicitly given in Letters:281) > edela > edel. Later Tolkien reconstructed the primitive form of Quenya Elda as eldâ (WJ:360); whether this could regularly yield Nandorin edel is doubtful, unless final -ld metathesized to -dl and a vowel developed to break up this final cluster.
In Etym, Tolkien first gave the Nandorin form as elda, then changed it. *Eledâ could not yield elda, since final -â is regularly lost in Nandorin. Since in this word we do not see loss of the second of two identical vowels (compare golda), we must conclude that final -a was lost before this could happen.
The primitive form of Quenya Noldo (and hence also Nandorin golda) is given in WJ:364, 380 as ñgolodô. This example demonstrates that in Nandorin, like in Quenya, the second of two identical vowels in adjacent syllables is lost in words that had another syllable following the lost vowel. This word alone provides a clear example of the change of primitive final _-ô to -a_. The form golda also suggests that in Nandorin as in Sindarin, the original initial nasalized stops ñg, nd, mb were simplified to g, d, b, though examples for d and b are lacking in our very small corpus. The stems involved are found in LR:377: ÑGOL "wise" and the extended form ÑGOLOD "one of the wise folk". Ñgolodô is thus either formed from ÑGOL by ómataina (suffixed base-vowel), suffixed D and the nominal (often masculine or agental) ending -ô, alternatively simply the longer ending -dô (of similar meaning) suffixed to the ómataina-form of the stem ÑGOL (sc. ñgolo-).