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1540s, "matter which settles at the bottom of water or other liquid," from Middle French sédiment (16c.) and directly from Latin sedimentum "a settling, sinking down," from stem of sedere "to settle, sit" (see sedentary).
sediment sed·i·ment (sěd'ə-mənt)
Insoluble material that sinks to the bottom of a liquid, as in hypostasis.