enclave (n.)

"small portion of one country which is entirely surrounded by the territory of another," 1868, from French enclave, from Old French enclaver "enclose, comprise, include" (13c.), from Late Latin inclavare "shut in, lock up," from Latin in- "in" (from PIE root *en "in") + clavis "key" (see slot (n.2)). Enclaved "surrounded by land owned by another" is attested in English from mid-15c., from Old French enclaver.