also block-buster, 1942, "large bomb" (4,000 pounds or larger, according to some sources), from block (n.1) in the "built-up city square" sense, + agent noun from bust (v.), on the notion of the widespread destruction they could cause. Entertainment sense "spectacularly successful production" is attested by 1952. U.S. sense of "real estate broker who sells a house to a black family on an all-white neighborhood," thus sparking an exodus, is from 1955.
1670s, "piece of wood, block" (especially one used to prevent movement), possibly from Old North French choque "a block" (Old French çoche "log," 12c.; Modern French souche "stump, stock, block"), from Gaulish *tsukka "a tree trunk, stump."