Meaning of BY in English
( a. )
Out of the common path; aside; -- used in composition, giving the meaning of something aside, secondary, or incidental, or collateral matter, a thing private or avoiding notice; as, by-line, by-place, by-play, by-street. It was formerly more freely used in composition than it is now; as, by-business, by-concernment, by-design, by-interest, etc.
Webster's Revised Unabridged English Dictionary. Пересмотренный полный словарь английского языка Webster. 2012