Roy C. Flickinger, The Greek theater and its drama (1918)
“ It is plain that in all or practically all of these the god is raised above the other performers, as would be only appropriate for an effective close; but whether the deity merely came forward upon the logium or was brought into view by means of a machine is not always an easy matter to determine. By a natural extension of meaning, however, such an apparition at the close of a play came to be called a “god from the machine” (θεὸς ἀπὸ μηχανῆς; deus ex machina) regardless of the method used for his appearance. ”
