both – оба, обе, так и…

both (adj., pron.) (есть несколько теорий, объясняющих это слово, все они выводят его из особенности говорить «как»).
there are several theories, all similar, and deriving the word from the tendency to say "both the." One is that it is Old English begen (masc.) "both" (from Proto-Germanic *ba, from PIE *bho "both") + -þ extended base. Another traces it to the Proto-Germanic formula represented in Old English by ba þa "both these," from ba (feminine nominative and accusative of begen) + þa, nominative and accusative plural of se "that." A third traces it to Old Norse baðir "both," from *bai thaiz "both the," from Proto-Germanic *thaiz, third person plural pronoun. Cf. similar formation in Old Frisian bethe, Dutch beide, Old High German beide, German beide, Gothic bajoþs.

1675:
BOTH (from Butu, Sax. from “be” and “tu”, “two”) the one and the other. Быть + два
Как видите, все проще и без всяких теорий. Практически русское выражение «оба два».