-ք

Etymology
From. The in  and other words ending in  developed from, through the regular sound change  → ; thus  → 🇨🇬.

Etymology
The origin is. What follows is Matasović’s summary of opinions, word for word (adjusted for Wiktionary style).

"Some scholars (e.g. Meillet and Godel) take the obvious course and derive it from [the masculine-feminine plural nominative case ending], but the sound development of word final *-s to *-kʿ is not universally accepted, though it may be supported by the development of PIE (🇨🇬) > Arm., and  > Arm. . Other linguists assume a pronominal particle added to the bare stem, but the origin of that particle has never been explained. A recent hypothesis derives the morpheme *-kʿ- from the agglutinated ; it would have been originally a dual marker, subsequently replacing the inherited plural. It is worth noting another possibility, although it is a mere speculation: the plural marker *-kʿ can be regularly derived from, with the ending of the u-stems  agglutinated to the regular Nom[inative] plural marker  (cf. the Vedic agglutinated Nom[inative] pl[ural] in -ās-as, e.g. )."