Etymology and linguistics can be quite beautiful, as well as confusing.
Last night, as I was falling asleep, I had one of those hazy epiphanies when you dart out of bed and scribble furiously on the closest napkin.
The main character in Oak and Thunder is named "Ylai". (Whether it's her birth name, or a nickname, I've not yet decided.)
The Tocharian (an IE language that's thought to be spoken by the Yuezhi, or their descendants) word "ylaiñäkte" is commonly translated as "Indra" (Hindu god of Thunder and other things, certainly one of the many related IndoEuropean thunder gods). The etymology isn't entirely clear, but it's thought the -ñäkte part stands for "god" and "ylai" is related to various other words for "smite" or "hit".
That makes Ylai a "Smiter".
Now, in the book "Perun: God of Thunder", Czech scholar Michal Téra examines the various aspects of thunder god worship among Slavic people. Interestingly, one of the Christianized versions of Perun (and other Slavic thunder deities) was Saint Elijah. In Russian - Ilya.
How good is that?! Ylai, Ilya...
Unfortunately, the two names aren't related. Ilya is a Russian version of Eliyahu, meaning "My God is Yahweh (in Hebrew).
I'd love for there to be an etymological connection - Téra mentions the association of thunder worship and Elijah started in early Christianity in the eastern Mediterranean, from where it came to the Balkans and to the Slavs. Unfortunately, most IE roots for thunder gods are entirely different and don't seem to relate in any way. (*trHon - thunder, *perk- and *per- for oak, smite, thunder or mountain)
Tocharian seems to be quite isolated in this regard:
"B ylai- and A wlā- would reflect PTch *w'älā(i̯än)-, in turn from PIE *wel(hx)eha-(h1en)- ... Semantically more likely, given the connection with storms (see ylaiñeṣṣe), however, is a derivation from*welh2-eha- ‘Smiter’ from *welh2- ‘strike’ [: Hittite walh- ‘strike’ and perhaps, with s-extension, TchB wālts- ‘trample’]."
It's far more likely the association was made thanks to attributes Elijah already had in the Old Testament - "he raised the dead, brought fire down from the sky, and was taken up "by a whirlwind.".
Raising the dead and fire from the sky are very common things for a thunder god to do.
Sometimes an epiphany ends in disappointment.