Английский Этимологический словарь - exact (adj.)

- 1380 (as exaction), from L. exactus, pp. of exigere, lit. "to drive or force out," also "demand, finish, measure," from ex- "out" + agere "drive, lead, act." The verb (1529) represents the literal sense of the Latin. Exacting "too demanding" is from 1583. Elliptical use of exactly for "quite right" not recorded before 1869.