The parts of a ship's hull that are above the waterline and don't contribute to buoyancy.
From 'dead' (inactive, without effect) + 'works' (constructed parts). In nautical terminology, 'dead' referred to parts that didn't participate in the ship's floating capacity, evolving from 16th-century maritime language.
Shipbuilders used this term because these upper hull sections literally 'do nothing' for floating—they're dead weight in terms of buoyancy! It's a perfect example of how technical jargon often uses everyday words in precise, logical ways.
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