Privative adjectives *ubogъ (“poor, miserable”) and *nebogъ (“poor, miserable”), as well as the later derivation *bogatъ (“rich”) prove that *bogъ was originally also an adjective meaning "earthly wealth/well-being; fortune", with a semantic shift to "dispenser of wealth/fortune" and finally "god". Semantic parallel can be drawn to Indo-Iranian languages: compare Old Persian 𐏎 (baga, “god”), Avestan [script needed] (baγa-, “god”) (but also [script needed] (bag-, “apportion”)), as well as Sanskrit epithet often applied to gods भग (bhaga, “dispenser, gracious lord, patron”), proving that Slavic noun had both abstract and concrete meanings. The same Iranian source, but via a Turkic language, also probably gave Proto-Slavic *banъ. Compare also Avar бакъ (baq̇̄, “sun”).
This convincing parallel has led some linguists (e.g. Roman Jakobson) to claim that *bogъ is an Iranian borrowing. Slavic-Iranian parallelism can be further extended to the expressions of Slavic mythology: Dažbog, Belobog and Chernobog, which suggest an existence of Iranian-type dualism in Proto-Slavic mythology.
Some connect it to Ancient Greek ἔφαγον (éphagon, “to eat, devour”) via a semantic shift "I received a share" > "I consumed" > "I ate". This would in turn all derive from the Proto-Indo-European root *bʰeh₂g-, *bʰag- (“to distribute, divide”).
- Derksen, Rick (2008) Etymological Dictionary of the Slavic Inherited Lexicon (Leiden Indo-European Etymological Dictionary Series; 4), Leiden, Boston: Brill, ISBN 978 90 04 15504 6, page 50
- Trubačev O. N., editor (1975), “*bogъ”, in Etimologičeskij slovarʹ slavjanskix jazykov [Etymological dictionary of Slavic languages] (in Russian), volume 02, Moscow: Nauka, page 161
- Skok, Petar (1971) Etimologijski rječnik hrvatskoga ili srpskoga jezika (in Serbo-Croatian), volume I, Zagreb: JAZU, page 178ff
- Mallory, J. P.; Adams, D. Q., editors (1997) Encyclopedia of Indo-European culture, London, Chicago: Fitzroy Dearborn Publishers, page 161
- Beekes, Robert S. P. (2010) Etymological Dictionary of Greek (Leiden Indo-European Etymological Dictionary Series; 10), volume II, with the assistance of Lucien van Beek, Leiden, Boston: Brill, page 1543
- Rix, Helmut, editor (2001) Lexikon der indogermanischen Verben [Lexicon of Indo-European Verbs] (in German), 2nd edition, Wiesbaden: Dr. Ludwig Reichert Verlag, ISBN 3-89500-219-4, page 65
- Fasmer, Maks (1964–1973), “бог”, in Etimologičeskij slovarʹ russkovo jazyka [Etymological Dictionary of the Russian Language] (in Russian), translated from German and supplemented by Trubačev O. N., Moscow: Progress