By

As a preposition, it can mean 'near,' 'through the action of,' or 'no later than,' as in 'by the door,' 'written by her,' or 'by Monday.' As an adverb, it can mean 'past' or 'aside,' as in 'walked by.'

From Old English 'bi' meaning 'near, about, alongside.' It is part of a very old family of little direction words in Germanic languages. Through time, its sense of nearness grew into ideas of agency ('done by') and deadline ('by Friday').