1560s, "a chafing, rubbing," from Middle French friction (16c.) and directly from Latin frictionem (nominative frictio) "a rubbing, rubbing down," noun of action from past participle stem of fricare "to rub, rub down," which is of uncertain origin. Watkins suggests possibly from PIE root *bhreie- "to rub, break." De Vaan suggests a PIE bhriH-o- "to cut" and compares Sanskrit bhrinanti, Old Church Slavonic briti "to shave." Sense of "resistance to motion" is from 1722; figurative sense of "disagreement, clash, lack of harmony, mutual irritation" first recorded 1761. Related: Frictional.