attrition (n.)

early 15c., "a breaking;" 1540s, "abrasion, scraping, the rubbing of one thing against another," from Latin attritionem (nominative attritio), literally "a rubbing against," noun of action from past-participle stem of atterere "to wear, rub away," figuratively "to destroy, waste," from assimilated form of ad "to" (see ad-) + terere "to rub" (from PIE root *tere- (1) "to rub, turn").

The earliest sense in English is from Scholastic theology (late 14c.), "sorrow for sin merely out of fear of punishment or a sense of shame," an imperfect condition, less than contrition or repentance. The sense of "wearing down of military strength" is from World War I (1914). Figurative use by 1930.