Probably from -ja (agent suffix) + -as.
-ias (front vowel harmony variant -iäs, linguistic notation -iAs)
From -i (adjective-forming suffix) + -as (adjective-forming suffix).
-ias
| Inflection of -ias | ||
|---|---|---|
| singular | plural | |
| nominative | -ias | -iasak |
| accusative | -iasat -iast |
-iasakat |
| dative | -iasnak | -iasaknak |
| instrumental | -iassal | -iasakkal |
| causal-final | -iasért | -iasakért |
| translative | -iassá | -iasakká |
| terminative | -iasig | -iasakig |
| essive-formal | -iasként | -iasakként |
| essive-modal | — | — |
| inessive | -iasban | -iasakban |
| superessive | -iason | -iasakon |
| adessive | -iasnál | -iasaknál |
| illative | -iasba | -iasakba |
| sublative | -iasra | -iasakra |
| allative | -iashoz | -iasakhoz |
| elative | -iasból | -iasakból |
| delative | -iasról | -iasakról |
| ablative | -iastól | -iasaktól |
| non-attributive possessive - singular |
-iasé | -iasaké |
| non-attributive possessive - plural |
-iaséi | -iasakéi |
(This etymology is missing or incomplete. Please add to it, or discuss it at the Etymology scriptorium.)
-iās
From Proto-Balto-Slavic *-jas; which also gave Latvian -̧s, -̧š – compare žálias : zaļš (“green”); tùsčias : tukšs (“empty”). Also related is the Proto-Slavic masculine *-ь. Ultimately, a thematised variant of i-stems (see -is), either of Proto-Indo-European age (cf. *-yós), or of more recent formation. Under stress, *-iós gave Lithuanian -ỹs; see for more.
-ias
(nouns):
| singular (vienaskaita) | plural (daugiskaita) | |
|---|---|---|
| nominative (vardininkas) | -ias | -iai |
| genitive (kilmininkas) | -io | -ių |
| dative (naudininkas) | -iui | -iams |
| accusative (galininkas) | -ią | -ius |
| instrumental (įnagininkas) | -iu | -iais |
| locative (vietininkas) | -yje | -iuose |
| vocative (šauksmininkas) | -iau | -iai |