early 14c., "to train or instruct in some specific subject," from Old French informer, enformer "instruct, teach" (13c.) and directly from Latin informare "to shape, give form to, delineate," figuratively "train, instruct, educate," from in- "into" (from PIE root *en "in") + formare "to form, shape," from forma "form". Sense of "communicate facts or news" first recorded late 14c.
Source: https://www.etymonline.com/word/inform