1325-75;Middle Englishborow, earlier burh, apparently gradational variant of late Middle Englishberi burrow, variant of earlier berg refuge, Old Englishgebeorg, derivative of beorgan to protect; akin to Old Englishburgen grave, i.e., place of protection for a body; see bury
"rabbit-hole, fox-hole, etc.," c.1300, borewe, from O.E. burgh "stronghold, fortress" (see borough); influenced by bergh "hill," and berwen "to defend, take refuge." The verb is first attested 1614. Related: Burrowed; borrowing.