block: [14] English borrowed block from Old French bloc, but its ultimate origin appears to be Germanic; French acquired it from Middle Dutch blok ‘tree trunk’. The derived verb block ‘impede’ first crops up in the early 15th century, but was not established until the later 16th century; it originally meant ‘put blocks [of wood] or obstacles in the way of’. Blockade was coined in the 17th century, perhaps on the model of ambuscade, a contemporary synonym of ambush. => blockade
