"belief in the existence of a personal God, generally accompanied by denial of revelation and the authority of a church," 1680s (deist is from 1620s), from French déisme, from Latin deus "god," from PIE root *dyeu- "to shine," in derivatives "sky, heaven, god."
A type of rationalistic theology that rose to prominence in England in the late 17c. and early 18c.; the deists advocated for the sufficiency of natural religion, apart from Scripture or revelation. Until c. 1700, the word was opposed to atheism; later it was the opposite of theism (q.v.), with which it is etymologically equivalent.
The term "deism" not only is used to signify the main body of the deists' teaching, or the tendency they represent, but has come into use as a technical term for one specific metaphysical doctrine as to the relation of God to the universe, assumed to have been characteristic of the deists, and to have distinguished them from atheists, pantheists and theists,—the belief, namely, that the first cause of the universe is a personal God, who is, however, not only distinct from the world but apart from it and its concerns. [Encyclopaedia Britannica, 1922]