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.