The earliest known use of the noun thing is in the Old English period (pre-1150). thing is a word inherited from Germanic.

thing (n.) Middle English thing, from Old English þing, þingc "meeting, assembly, council, discussion," also "action, deed to be done." In late Old English, "concrete inanimate object; that which exists by itself; entity, being, creature;" also "event."

"The ancestral meaning of thing is time: it goes back to a prehistoric Germanic *thingam, which was related to Gothic theihs time, and may come ultimately from the Indo-European base *ten stretch (source of English tend, tense, etc). In Germanic it evolved semantically via appointed time to judicial or legislative assembly.

I would describe the etymology of ‘thing’ to be hilariously pathetic as would you when you read the whole story behind the word. Thing, as such, first appeared as the Proto-Indo-European root *tenkó-, and it roughly meant “span” or “extend”. This root stretches probably far back to the possible ancestor *tenk-, which meant “to suit” or “to fit”.