The word *wĺ̥kʷos is a thematic accented zero-grade noun perhaps derived from the adjective *wl̥kʷós (“dangerous”); compare Hittite 𒉿𒀠𒆪𒉿𒀸 (walkuwa-, “something negative”), Old Irish olc (“evil”), Sanskrit अवृक (avṛká, “safe”, literally “not wild”), वृकतात् (vṛká-tāt, “savagery”). Stress shift onto the zero-grade is consistent with nominalized adjectives: compare Sanskrit कृष्ण (kṛ́ṣṇa, “black antelope”) from कृष्ण (kṛṣṇá, “black”). Alternatively, the word may be a derivative of the verbal root *welh₂- (“to tear up”). In either case, the word's formation closely resembles that of *h₂ŕ̥tḱos (“bear”), another thematic accented zero-grade noun whose referent is an animal subject to cultural taboos.
The Latin and Greek reflexes are unexpected (vs. expected Lat *volquus, Gk *álpos, according to the regular progression PIE *l̥ > Lat ol, Gk al). The Latin reflex is a borrowing from Osco-Umbrian (where PIE */kʷ/ regularly gave /p/), and both the Italic and Greek reflexes underwent metathesis, possibly as a taboo deformation meant to offset the fear usually associated with the animal. A deformation would explain the metathesis of */w/ and */l/, which also occurred in Greek (*wĺ̥kʷos → *lúkʷos → λύκος (lúkos)), and also explains the presence of delabialized /k/ per the boukólos rule (regardless of whether it is Proto-Indo-European already or only Proto-Greek). In both cases, the expected forms are so close to the word for “fox” – compare Latin volpēs, Ancient Greek ἀλωπός (alōpós), ἀλώπηξ (alṓpēx) – that avoiding conflation of the two words “wolf” and “fox” may have motivated either alteration or borrowing.
The Germanic reflex, with /f/ < */p/ < */kʷ/, underwent an unusual sound change, but the velar was retained in at least one form, i. e. Old Norse ylgr (“she-wolf”) (vs. Old English wylf, Middle High German wülpe < *wulbi) < *wulgʷī́ < *wl̥kʷíh₂s, which indicates neither taboo deformation nor derivation from some other root took place.
Armenian and Celtic have replaced the word with Proto-Indo-European *waylos (“howler”) due to taboo; compare Old Armenian գայլ (gayl), Middle Irish fáel. (In Celtic, *kū (“hound, dog”) is also used to designate the wolf.)
- *wl̥kʷíh₂s (“she-wolf”)
- Proto-Albanian: *ulka-
- Proto-Balto-Slavic: *wilkás (see there for further descendants)
- (possibly) Proto-Celtic: *ulkos (see there for further descendants)
- Proto-Germanic: *wulfaz (see there for further descendants)
- Proto-Hellenic: *lúkos
- Proto-Indo-Iranian: *wŕ̥kas (see there for further descendants)
- Proto-Italic: *lukʷos
- → Latin: lupus (see there for further descendants)
- Paeonian: Λυκκ- (Lukk-), Λυκπ- (Lukp-) (< *lukʷos)
- Proto-Tocharian: *wä́lkʷë
- Tocharian B: walkwe
- ^ A. Lehrman, “Anatolian Cognates of the PIE Word for ‘Wolf’”, Die Sprache 33 (1987), 13–18.
- ^ Tamaz Gamkrelidze & Vjačeslav Ivanov, Indo-European and the Indo-Europeans (Tbilisi: Tbilisi UP, 1984), 492.
- ^ Mallory, J. P.; Adams, D. Q., editors (1997), “*wolf”, in Encyclopedia of Indo-European culture, London, Chicago: Fitzroy Dearborn Publishers, page 646
- ^ Martirosyan, Hrach (2010) Etymological Dictionary of the Armenian Inherited Lexicon (Leiden Indo-European Etymological Dictionary Series; 8), Leiden, Boston: Brill, page 196.