-օղ

• -աւղ (-awł)
• -ող (-oł)

The original spelling is -աւղ (-awł), from Proto-Indo-European *-tlo-, a thematic form of the *-tel- suffix, with a preceding *-ā or *-ə. Compare ծնօղ (cnōł) from Proto-Indo-European *ǵenətlo-. Cognate with Proto-Slavic *-teľь.

The spelling -ող (-oł) is either an early monophthongized version of -աւղ (-awł) or has another origin, perhaps Proto-Indo-European *-olo-, *olā-; compare the ending of Ancient Greek μαινόλης (mainólēs), φαινόλης (phainólēs).

The endings of ձախող (jaxoł), յաջող (yaǰoł), խճող (xčoł) may be different from this suffix; they may be of Urartian origin.

-օղ • (-ōł)

1. Forming adjectives and agent nouns from verbs.

Armenian grammarians assign to this a function of a participial suffix. But Old Armenian forms in -օղ (-ōł) are not participles and they do not belong to the conjugation. Old Armenian had only one true participle, formed with -եալ (-eal). In modern Armenian -ող (-oł), indeed, forms participles.

• Armenian: -ող (-oġ)

• Ačaṙyan, Hračʻya (1940) Hayocʻ lezvi patmutʻyun [History of the Armenian Language] (in Armenian), volume I, Yerevan: University Press, page 31
• Gočanean, Pōġos (2011) Dasakan grabari gorcnakan kʻerakanutʻiwn [Practical Grammar of Classical Old Armenian]‎ (in Armenian), Vienna and Yerevan: Mekhitarist Press, page 65
• Godel, Robert (1975) An introduction to the study of classical Armenian, Wiesbaden: Dr. Ludwig Reichert Verlag, page 37
• J̌ahukyan, Geworg (1998) “-աւղ”, in Hin hayereni verǰacancʻneri cagumə [The Origin of Old Armenian Suffixes] (Hayocʻ lezvi hamematakan kʻerakanutʻyan harcʻer; 2) (in Armenian), Yerevan: Anania Širakacʻi, pages 5–48