ergative

How is this casename composed? Other casenames have Latin ppp stems
in them from verbs nominare, vocare, accusare, dare, auferre, (col)
locare, gignere ... But I know of no verb ergare.
Is it formed from the preposition erga, towards, vis-à-vis?
Or is it Gr. ergon?
Does somebody know who coined this term and when?
Regards
Lars