Traditionally derived from ἐρῠθρός +‎ Proto-Indo-European *pel- 'to cover, wrap; skin, hide; cloth'; compare πέλμᾰ 'sole of foot' and Latin pellis 'a skin, hide, felt, pelt'. According to Beekes, it may also be of Pre-Greek origin, comparing the first element of the word with the first element of ἐρῠσῑ́βη 'rust in plants' and ἐρῠσῐ́σκηπτρον 'kind of plant'.

Beekes, Robert S. P. (2010) Etymological Dictionary of Greek (Leiden Indo-European Etymological Dictionary Series; 10), with the assistance of Lucien van Beek, Leiden, Boston: Brill, page 467