transaction (n.)

mid-15c., "the adjustment of a dispute, a negotiated agreement, management or settlement of an affair," from Old French transaccion "exchange, transaction," from Late Latin transactionem (nominative transactio) "an agreement, accomplishment," noun of action from past participle stem of transigere "stab through; accomplish, perform, drive or carry through, come to a settlement," from trans "across, beyond; through" (see trans-) + agere "to set in motion, drive, drive forward," hence "to do, perform" (from PIE root *ag- "to drive, draw out or forth, move"). Meaning "a piece of business" is attested from 1640s. Related: Transactions; transactional.