A worker, a maker, a creator; specifically. God.
Mid 17th century; earliest use found in John Bulwer (bap. 1606, d. 1656), medical practitioner and writer on deafness and on gesture. From classical Latin opific-, opifex craftsman, artisan, inventor, used in both pagan and (in post-classical Latin) Christian writers of the creator of the world from op-, base of opus work + -i- + -fic-, -fex, combining form of facere to do, make.