discount

Discount comes from French descompte/décompte, from Old French disconter/desconter ("reckon off, account back"), from Medieval Latin discomputō ("to deduct, discount"), built from Latin dis- ("away") plus computō ("to reckon, count").

The word has carried the sense of deducting or reckoning away from the start, from Medieval Latin discomputō through French into English, keeping its 'take away by counting' meaning intact.

Its surface analysis in English breaks down neatly as dis- plus count, echoing the same computō root that gave Latin its 'reckon' sense.