1570s, "subtract," from Latin subductus, past participle of subducere "to draw away, take away" (see subduce). Geological sense is from 1971, a back-formation from subduction. Related: Subducted; subducting.
early 15c., "withdrawal, removal" (originally of noxious substances from the body), from Latin subductionem (nominative subductio) "a withdrawal, drawing up, hauling ashore," noun of action from past participle stem of subducere "to draw away, take away" (see subduce). Geological sense is attested from 1970, from French (1951).
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Harper, D. (n.d.). Etymology of subduct. Online Etymology Dictionary. Retrieved $(datetime), from https://www.etymonline.com/word/subduct