There are four theories about its origin:
- Either from Old High German kenning (“symbol, sign”) or from other Germanic source (compare Gothic 𐌺𐌿𐌽𐌽𐌰𐌽 (kunnan, “to know”) and Old Norse kunna (“to know”)).
- Alternatively, from Akkadian 𒁾 (kunukku, “seal-cylinder, kunukku”) or [script needed] (kanikku, “sealed object: document, sack bulla, etc.”), via Old Armenian կնիք (knikʿ, “seal”) and Turkic.
- A Chinese origin, from 卷 (Middle Chinese /kɣiuᴇnX, kɣiuᴇnH/ < Old Chinese /*krorʔ/ ("to roll up"), /*kror-s/ ("scroll")) via Turkic küiniŋ, has also been suggested, as paper was invented in China in about the 1st century AD. However this seems less likely, due to the likely temporal precedence of Proto-Slavic over Early Middle Chinese and the large spatial separation of the donor and recipient languages. Speaking in favor of this etymology is, however, Hungarian könyv (“book”) (reflecting hypothetical Pre-Hungarian *künig), which is much more clearly derived from Turkic küiniŋ and cannot be derived from the Slavic forms.
- Finally, Polish slavist Aleksander Brückner considers it to be a native word derived from Proto-Slavic *kъnъ (“trunk of a tree”) with the suffix -iga (compare Slovene veriga (“chain”), from Proto-Indo-European *ver- (“tie”)). The sense development would thus be similar to German Buch and English book, from Proto-Indo-European *bʰeh₂ǵos (“beech”), or to Latin liber, from earlier *luber, a cognate of Proto-Slavic *lubъ (“tree bark”).
Declension of *kъnjiga (hard a-stem)
- East Slavic:
- South Slavic:
- West Slavic:
- “книга” in Max Vasmer (1986), Etimologičeskij slovarʹ russkogo jazyka [Etymological Dictionary of the Russian Language], in 4 vols (second edition), Moscow: Progress — Translated from German and supplemented by O. N. Trubačóv
- “*kъniga” in Oleg Trubačóv (ed.) (1974–), Etimologičeskij slovarʹ slavjanskix jazykov [Etymological dictionary of Slavic languages], Moscow: Nauka, volume 13, page 203f
- “книга” in Galina Cyganenko (1989), Etimologičeskij slovarʹ russkogo jazyka [Etymological Dictionary of the Russian Language], (2nd ed.), Kiev: Radyanska Shkola, page 179–180
- “книга” in Pavel Černyx (1999), Istoriko-etimologičeskij slovarʹ russkogo jazyka [Historical-Etymological Dictionary of the Russian Language], in 2 vols (3rd ed.), Moscow: Publishing House "Russian Language", volume 1, page 406
- “ḱinyg | kinugæ, kiwnugæ” in Vasilij Abajev (1958–89), Istoriko-etimologičeskij slovarʹ osetinskogo jazyka [Historical-Etymological Dictionary of Ossetian], in 4 vols, Moscow–Leningrad: USSR Academy of Sciences, volume 1, page 596
- “կնիք” in Hračʿeay Ačaṙean (1971–79), Hayerēn armatakan baṙaran [Dictionary of Armenian Root Words], in 4 vols (second edition), Yerevan: Yerevan State University, volume 2, page 609