Gloss: ‘curdled milk, curds’ (item 125 in Bjørn 2017)
Attestations: Rus. tvaróg ‘quark’; Gr. τῡρός ‘curdled milk’; Ved. tuvara- ‘astringent’, Av. tūiri
Attestations only pertinent for the Graeco-Aryan and Slavic branchings, this produce term nonetheless appears to be reconstructable for late or late middle PIE. On the somewhat discontinuous semantics in Vedic, it may be noted that Middle Indic continuations retain the meaning ‘cheese’ (Turner 1966: 336). A case for an internal verbal derivational basis has not been satisfactorily posited (cf. Mallory & Adams 1997: 382f.). The phonetic structure is void of phonemes that represent the telltale developments of the pertinent dialects, and a wanderwort phenomenon cannot formally be excluded; the modern English word quark is similarly assumed to have traveled from Slavic through Middle High German.
North Caucasian: *ˀV-twVr– ‘to become rolled up, turn sour, rot, putrefy’ > e.g. Archi tar-as ‘to roll up (of milk)’
Discussion: A North Caucasian origin of this term, as suggested by (S. Starostin 2009: 102) seems rather attractive as a technical term that emanated from the Caucasus, where the verbal derivational basis is transparent. The prefix here has to be discarded to fit the IE attestations, but this seems a minor problem; verbal roots normally interact more extensively with prefixes than nominals do (cf. Nikolayev & Starostin 1994: 82ff.). The possible linguistic fixpoints allow for a very concrete chronological hypothesis: The item likely departed from North Caucasian and entered either late PIE or, alternatively, differentiated IE languages still in close contact, and lastly reached the Germanic languages through Slavic.