1620s, "reckon as an abatement or deduction" (a sense now obsolete), from Old French desconter "reckon off, account back" (13c., Modern French décompter), from Medieval Latin discomputare, from dis- "away, from" (see dis-) + computare "to reckon, to count" (see compute). Hence, "to abate, deduct" (1650s), and figurative sense "to leave out of account, disregard" (1702). Formerly also discompt. Commercial sense of "make a deduction from, put a reduced price upon" is by 1977. Related: Discounted; discounting.