A Quenya noun for “lily” or more generally any “large flower”, cognate of Ad. inzil.

Conceptual Development: This word appeared in two forms with competing etymologies. In the early 1950s, it appeared as Q. insil, a loan word from Atani inzil, where the [nz] became [ns] (PE19/99). A similar word indil appeared in the 1959-60 essay Quendi and Eldar, where it was a derivative of Valarin iniðil (WJ/399), with the middle i lost due to the Quenya syncope and then the spirant [ð] becoming the stop [d] after the nasal [n].

In the second scenario, Tolkien did not directly connect Q. indil to Ad. inzil, but the coincidence of forms is too great: Tolkien must have imagined a reverse loan from Valarin > Quenya > Atani. Perhaps this loan took place before the [ð] became [d] in Quenya ([nð] > [nd]), and the voiced spirant was adapted as the sibilant [z] in Atani because that language did not possess spirants in its earliest historical stages.

I personally prefer this second scenario and the form indil, because using the first scenario would require discarding one of our few Valarin words (iniðil).