The origin of "everything": Late 14th Century, from every and thing.<quoted text>
what theories have you swallowed regarding the origin of eveything, who wrote them and why do you believe those people???
"Every": early 13c., contraction of Old English æfre ælc "each of a group," lit. "ever each" (Chaucer's everich), from each with ever added for emphasis, as the word is still felt to need emphasis.
"Thing": Old English þing "meeting, assembly," later "entity, being, matter" (subject of deliberation in an assembly), also "act, deed, event, material object, body, being," from P.Gmc.*thengan "appointed time" (cf. Old Frisian thing "assembly, council, suit, matter, thing," Middle Dutch dinc "court-day, suit, plea, concern, affair, thing," Dutch ding "thing," Old High German ding "public assembly for judgment and business, lawsuit," German ding "affair, matter, thing," Old Norse þing "public assembly"). Some suggest an ultimate connection to PIE root *ten- "stretch," perhaps on notion of "stretch of time for a meeting or assembly."