by – около, рядом, возле, у; мимо; до, к (время); средство (с помощью чего – by email); с помощью (исполнителя, автора – by Shakespeare; кстати, между прочим – by the way.
by (prep.) (староанглийское «be-» (безударный) или «bi» - ударный); около, в, мимо, в течение, рядом; из протогерманского *bi от *umbi (связано со второй состовляющей PIE корня *ambhi – вокруг, много, со всех сторон.
Old English be- (unstressed) or bi (stressed) "near, in, by, during, about," from Proto-Germanic *bi "around, about" (cf. Old Saxon and Old Frisian bi "by near," Middle Dutch bie, Dutch bij, German bei "by, at, near," Gothic bi "about"), from *umbi (cognate with second element in PIE *ambhi "around," cf. Sanskrit abhi "toward, to," Greek amphi- "around, about;" see ambi-).

Originally an adverbial particle of place, in which sense it is retained in place names (Whitby, Grimsby, etc.). Elliptical use for "secondary course" (opposed to main; e.g. byway, also cf. by-blow "illegitimate child," 1590s) was in Old English. This also is the sense of the second by in the phrase by the by (1610s). By the way literally means "in passing by" (mid-14c.); used figuratively to introduce a tangential observation by 1540s.

Phrase by and by (early 14c.) originally meant "one by one," modern sense is from 1520s. By and large (1660s) originally was nautical, "sailing to the wind and off it," hence "in one direction then another."

1675:
BY (Bi, Sax.) beside, or nigh. This word notes the Cause, the Agent, the Instrument, The Means and the Manner of Action. Кроме того или ближний, близкий. Это слово обозначает причину, представителя, инструмент. Означает образ действия.
BY or BYE (Bye of Bian, Sax. to dwell, an Habitation or Place; as Danby, Appleby etc. By and by, in a short Time. Обитать (саксонское); место обитания. В короткое время.
Короче говоря – это русское слово «быть», «быти».