borrow (v.) Look up borrow at Dictionary.com
Old English borgian "to lend, be surety for," from Proto-Germanic *borg "pledge" (source also of Old English borg "pledge, security, bail, debt," Old Norse borga "to become bail for, guarantee," Middle Dutch borghen "to protect, guarantee," Old High German boragen "to beware of," German borgen "to borrow; to lend"), from PIE root *bhergh- (1) "to hide, protect."

Sense shifted in Old English to the modern one, "take or obtain (something) on pledge to return it or security given," apparently on the notion of collateral deposited as security for something borrowed. Figurative use from early 13c.; borrowed time is from 1898. As an operation in subtraction, 1590s. Related: Borrowed; borrowing.