The word "double" (duplex) is derived, some authors hold, from the ancient custom of reciting two offices or saying two Masses on the same dayone for the current feria and one for the feast (festa).

<Ply, plic, plicate> (fold): (1) ply, reply, imply, plight, suppliant, explicit, implicit, implicate, supplicate, duplicate, duplicity, complicate, complicity, accomplice, application, plait, display, plot, employee, exploit, simple, supple; (2) pliant, pliable, replica, explication, inexplicable, multiplication, deploy, triple, quadruple, plexus, duplex.