transact (v.)
1580s, back-formation from transaction, or else from Latin transactus, past participle of transigere "to drive through, accomplish, bring to an end, settle," 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"). Related: Transacted; transacting.