Close-fitting and taut. The analogy is to the skin of the drumhead, which is tightly stretched so that when it is struck the drum sounds as it should. This term was transferred in the nineteenth century to anything stretched taut; Thomas Hughes (Tom Brown’s School Days, 1857) described his hero as having eaten so much that “his little skin is as tight as a drum.” In succeeding years, however, the analogy itself was sometimes to a drum-shaped container for liquids, such as an oil drum, which of course must be well sealed to prevent leakage. Hence the expression “tight as a drum” also became synonymous with “watertight,” as in “The shelter they rigged up was as tight as a drum.”