sameyoudaoicibaDictYouDict[same 词源字典]
same: [12] Same comes ultimately from Indo- European *somós ‘same’. This also produced Greek homós ‘same’ (source of the English prefix homo-, as in homosexual), and was a variant of the base that gave Latin similis ‘similar’ (source of English similar and simulate), Latin simul ‘at the same time’ (source of English assemble and simultaneous), Latin simplus ‘simple’ (source of English simple).

Latin singulus ‘single’ (source of English single and singular), and English seem and some. The Indo-European adjective passed into prehistoric Germanic as *samaz, which in due course evolved into Old Norse same. The Vikings brought the word with them to England, where it gradually replaced the native terms for ‘same’, ilk and self.
[same etymology, same origin, 英语词源]
same (adj.)youdaoicibaDictYouDict
perhaps abstracted from Old English swa same "the same as," but more likely from Old Norse same, samr "same," both from Proto-Germanic *sama- "same" (cognates: Old Saxon, Old High German, Gothic sama, Old High German samant, German samt "together, with," Gothic samana "together," Dutch zamelen "to collect," German zusammen "together"), from PIE *samos "same," from root *sem- (1) "one," also "as one" (adv.), "together with" (cognates: Sanskrit samah "even, level, similar, identical;" Avestan hama "similar, the same;" Greek hama "together with, at the same time," homos "one and the same," homios "like, resembling," homalos "even;" Latin similis "like;" Old Irish samail "likeness;" Old Church Slavonic samu "himself").

Old English had lost the pure form of the word; the modern word replaced synonymous ilk. As a pronoun from c. 1300. Colloquial phrase same here as an exclamation of agreement is from 1895. Same difference curious way to say "equal," is attested from 1945.