"the shutting up of a place by hostile ships or troops," 1690s, from block (v.1) + -ade, false French ending (the French word is blocus, 18c. in this sense, which seems to be in part a back-formation from the verb bloquer and in part influenced by Middle Dutch blokhuus; see blockhouse). Blockade-runner is from 1863.
"prevent ingress and egress from by warlike means," 1670s, from blockade (n.). Related: Blockaded; blockading.