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1795, "process of erosion," from Latin detritus "a wearing away," from detri-, stem of detere "wear away" (see detriment). Geological sense of "matter produced by erosion" is 1802, probably from French detritus; incorrect, in any case.
detritus de·tri·tus (dĭ-trī'təs)
n. pl. detritus
Loose matter resulting from the wearing away or disintegration of a tissue or substance.