The word *wĺ̥kʷos is a thematic accented zero-grade noun perhaps derived from the adjective *wl̥kʷós (“dangerous”) (compare Hittite 𒉿𒀠𒆪𒉿 (walkuwa, “dangerous”), 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; 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 → *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 alōpós, 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, e.g., Old Norse ylgr (“she-wolf”) (vs. Old English wylf, Middle High German wülpe ← *wulbī) ← *wulgʷī́ ← *wl̥kʷíh₂, 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.)
*wĺ̥kʷos m (non-ablauting)
- Old Albanian: ulk
- Albanian: ujk
- Luwian: 𒉿𒀠𒉿 (*walwa/i, “lion”) (only attested in personal names)
- Lydian: walw-el(i) "lion-like, pertaining to lions"
- Balto-Slavic: *wilkas (see there for further descendants)
- Slavic: *vьlkъ (see there for further descendants)
- Celtic: *ulkʷos (see there for further descendants)
- Germanic: *wulfaz (see there for further descendants)
- Indo-Iranian: *wŕ̥kas (see there for further descendants)
- Italic: *lukʷos
- Latin: lupus (possibly through Osco-Umbrian) (see there for further descendants)
- Paeonian: Λυκκ- (Lukk-), Λυκπ- (Lukp-) (< *lukʷos)
- 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.
- ^ J.P. Mallory & D.Q. Adams, Encyclopedia of Indo-European Culture, s.v. "wolf" (London: Fitzroy Dearborn, 1997), 646.
- ^ Martirosyan, Hrach (2010) Etymological Dictionary of the Armenian Inherited Lexicon (Leiden Indo-European Etymological Dictionary Series; 8), Leiden, Boston: Brill, page 196