Traditionally derived from Proto-Indo-European *pel- (“flour, dust”), with accompanying comparanda given in the box below.
Cognates
* Latin pollen
* Sanskrit पलाल (palāla)
* Ancient Greek πάλη (pálē, “dust, meal”)
* Albanian pluhur, Gheg Albanian pluhun (possibly)
* Lithuanian pelenai
* Russian пепел (pepel)
* Old Church Slavonic попелъ (popelŭ), пепелъ (pepelŭ)
However, De Vaan is skeptical and prefers a derivation from Proto-Indo-European *pelh₁- (“chaff”), comparing palea (“idem”); see there for more.