A noun in The Etymologies of the 1930s glossed “bride” derived from the root ᴹ√NDIS (EtyAC/NDIS). It was translate “wife” in the later phrase Q. Indis i·Ciryamo “The Mariner’s Wife” (UT/8), but I think this is a loose translation and “bride” is more accurate. In The Etymologies Tolkien gave two plural forms: inderi (which might be indesi) and indissi, the latter influenced by the plural ᴹQ. nissi for “women” (EtyAC/NDIS). I’d use the stem form indiss- for this word, to avoid awkward changes of the final consonant from s to r in inflected forms.
Neo-Quenya: In a post on 2024-09-27 in the Vinyë Lambengolmor Discord Server (VLDS), Luinyelle suggested it might also mean “fiancée”.
The second wife of Finwë (S/64-5). Her name is said to mean “great or valiant woman” (PM/343), but it is also identical in form to indis “wife, bride”.
Conceptual Development: The name Indis appeared in several places in The Etymologies from the 1930s glossed as “Bride” (Ety/I², NDIS, NETH), but there it seems to be a name for Nessa (Ety/NĪ¹). The number and names of the wives of Finwë were unspecified in Silmarillion drafts from the 1930s and 50s (LR/223, MR/175). Indis as the second wife of Finwë did not emerge until late in Tolkien’s writing (WJ/327, 383; PM/344).