togetheryoudaoicibaDictYouDict[together 词源字典]
together: [OE] The etymological notion underlying together is of ‘gathering’ things into one group. It was formed from the preposition to and the element *gad- denoting ‘association, company’, which also lies behind gather.
=> gather[together etymology, together origin, 英语词源]
together (adv.)youdaoicibaDictYouDict
Old English togædere "so as to be present in one place, in a group, in an accumulated mass," from to (see to) + gædere "together" (adv.), apparently a variant of the adverb geador "together," from Proto-Germanic *gaduri- "in a body," from PIE *ghedh- "to unite, join, fit" (see good, and compare gather).

In reference to single things, "so as to be unified or integrated," from c. 1300. Adjective meaning "self-assured, free of emotional difficulties" is first recorded 1966. German cognate zusammen has as second element the Old High German verbal cognate of English same (Old English also had tosamne "together").