There is also another and a greater necessity for our offering prayer in behalf of the emperors, nay, for the complete stability of the empire, and for Roman interests in general. For we know that a mighty shock impending over the whole earth— in fact, the very end of all things threatening dreadful woes— is only retarded by the continued existence of the Roman empire. We have no desire, then, to be overtaken by these dire events; and in praying that their coming may be delayed, we are lending our aid to Rome's duration. More than this, though we decline to swear by the genii of the Cæsars, we swear by their safety, which is worth far more than all your genii. Are you ignorant that these genii are called “Dæmones,” and thence the diminutive name “Dæmonia” is applied to them? We respect in the emperors the ordinance of God, who has set them over the nations. We know that there is that in them which God has willed; and to what God has willed we desire all safety, and we count an oath by it a great oath. But as for demons, that is, your genii, we have been in the habit of exorcising them, not of swearing by them, and thereby conferring on them divine honour.
Source: The Apology (New Advent)