enclave
Enclave (noun) means an area belonging to one group that lies entirely within territory controlled by another.
Etymology
Borrowed from French enclave, from Middle French enclave ("enclave"), a deverbal noun from enclaver ("to inclose"), from Old French enclaver ("to inclose, lock in"), from Vulgar Latin *inclāvāre ("to lock in"), from in plus Latin clavis ("key") or clavus ("nail, bolt"). Compare inlock.