Uncertain. Perhaps from Proto-Italic *knīdos or *kneydos, itself perhaps from Proto-Indo-European *knīdos or *knéyd-os. Sihler alternatively reconstructs a possible pre-form Proto-Italic *knīdōs. The term may ultimately derive from the root *kneyd- (“to scratch”). It is possible that a semantic connection between a word for "to sting" and "to stink" is paralleled in English stink and Gothic stigqan (“to clash”). The term may also be cognate with Homeric Ancient Greek κνίση (knísē, “smell of roasting fat”) and Attic κνῖσα (knîsa), but Beekes finds this phonetically unlikely. However, the linguist Stefan Höfler posits a pre-form *kníHd-ōs, itself from a root *kníHd-, which—according to Höfler—could unify the Greek and Latin forms.