There is an etymology commonly used in Hindutva circles, where it is argued that Indra will be a "bmac" deity, due to a loanword, from the bmac substratum. however, I have not found much basis for this claim other than Alexander Lubotsky. a quick search on the wiki reveals that there is not really a consensus on these claims.

there is a more plausible etymology for the character Indra's name, of PIE origin, Indra comes From PII *índras, being a conception as derivative of of the PIE *h3eyd-, meaning "to swell" or "to become strong." *(H)i-n-d-rá-s would mean "the strong" and underwent a secondary stress shift. This makes sense, since in the RV verses, indra receives an epithet related to "strong."
(Manfred Mayrhofer,
Etymologisches Wörterbuch des Altindoarischen)
https://archive.org/details/etymologischesworterbuchdesaltindoarischenmayrhoferewa11992rep_25_b