1943, in reference to grammatical case used for the subjects of transitive verbs (in Eskimo, Basque, Caucasian languages), from Greek ergatēs "workman," from combining form of ergon "work" (from PIE root *werg- "to do") + -ive.
It is the hypothetical source of/evidence for its existence is provided by: Greek ergon "work," orgia "religious performances;" Armenian gorc "work;" Avestan vareza "work, activity;" Gothic waurkjan, Old English wyrcan "to work," Old English weorc "deed, action, something done;" Old Norse yrka "work, take effect."
word-forming element making adjectives from verbs, meaning "pertaining to, tending to; doing, serving to do," in some cases from Old French -if, but usually directly from Latin adjectival suffix -ivus (source also of Italian and Spanish -ivo). In some words borrowed from French at an early date it has been reduced to -y (as in hasty, tardy).
<a href="https://www.etymonline.com/word/ergative">Etymology of ergative by etymonline</a>
Harper, D. (n.d.). Etymology of ergative. Online Etymology Dictionary. Retrieved $(datetime), from https://www.etymonline.com/word/ergative