The hard outer layer of bread; the outer edges or surfaces of something; or dried layers on a wound.
From Old French 'crouste' and Latin 'crusta' (shell, rind). Originally meant any hardened outer layer, from the image of a shell.
Crusts were once poor people's food—literally the scraps left after baking—but they became so associated with toughness and survival that 'earning your crust' means earning a living, linking food to class hierarchy!
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