lupus.

Uncertain. Possibilities include: * Ultimately from Proto-Indo-European *wĺ̥kʷos (“wolf”). The term may have undergone metathesis to Proto-Italic *lukʷos, which then may have entered Latin via a Osco-Umbrian language, where the change of *kʷ to /p/ is regular. Another example of a borrowing with that shift is popīna. According to the linguist Stefan Höfler, a non-metathesized Italic form may be reflected in Latin Ulpius. * Linguist Simon Esposito argues that, since Ancient Greek λύκος (lúkos) may showcase similar metathesis, the term was borrowed from an Osco-Umbrian language that itself may have borrowed the term from Greek at an early date. * De Vaan alternatively suggests a possible derivation from Proto-Indo-European *wl̥p / *lup- (“marten”), which is perhaps also continued by Latin vulpēs (“fox”). According to De Vaan, such a development may have occurred due to the tabooistic replacement of the word for “wolf.” However, De Vaan notes that this theory requires an explanation for the term’s continuance as vulpēs. This etymology also requires a somewhat tenuous semantic development from “marten” > “fox” > “wolf”. Possible cognates include Ancient Greek λύκος (lúkos), Sanskrit वृक (vṛka), Old English wulf, and Old Church Slavonic влькъ (vlĭkŭ). Doublet of lycos and Lycus.