Let's learn Quenya on the Downs

[Galadriel55]

I have been following along about as nimbly as Gimli on a horse. But I had a question, on reading on of the translations, because I thought I knew the word but I didn't:

Originally Posted by Huinesoron

I tengwar Eldarin, yára lé, apa i lambë i Mordoro ita sinomë váquetuvan quetë.

I saw "ita" and brain matched it to the Quenya form of Idril, IIRC meaning something like "sparkling" or "shining". Here it means "which". Is there a similar sounding root that is used for Idril, or did I make that up?