burrow (n.) Look up burrow at Dictionary.com
"rabbit-hole, fox-hole, etc.," c.1300, borewe, from Old English burgh "stronghold, fortress" (see borough); influenced by bergh "hill," and berwen "to defend, take refuge."
burrow (v.) Look up burrow at Dictionary.com
c.1600, "to place in a burrow, from burrow (n.). Figuratively (such as to burrow (one's) head) by 1862. Intransitive sense, "to bore one's way into, penetrate" is from 1610s, originally figurative (literal sense, of animals, attested by 1771). Related: Burrowed; borrowing.