Epitassō (ἐπιτάσσω) means to command with authority — to order, enjoin, charge. From epi (upon) + tassō (to arrange/appoint). It appears in the Gospels for Jesus commanding demons and sea-storms, and in Paul for legitimate authority.
When Jesus epitassō-es the demons and wind, Mark records the onlookers' astonishment: "He commands [epitassō] even the unclean spirits and they obey him!" (Mark 1:27). The command-obedience pattern reveals the order of reality: all things were made through the Logos; all things obey the Logos when he speaks with full authority. The demons obey; the sea obeys; even death obeys (Lazarus). Paul's use in Philemon 8-9 is deliberate contrast: though he could command (epitassō) Philemon, he appeals instead through love — modeling the authority that serves rather than compels.
Epitassō sits in the authority-language cluster with entellō (to command with instructions), keleuō (to command imperatively), and prostassō (to assign/command). Jesus's epitassō over demons is the most theologically loaded usage: it reveals what the kingdom means — God's authority reasserted over the rebel powers. The exorcism is not magic but the reinstatement of the divine order. Wherever Jesus commands, things become as they were meant to be.