word-forming element meaning "belief (of a specified kind) in God, a god, or gods," from Greek theos "god" (from PIE root *dhes-, forming words for religious concepts) + -ism.
"self-deification," 1610s, from auto- + -theism. The religion of one who mistakes his own inner voices for God's voice in him. Also used in a theological sense (1580s) for "the regarding of the second person of the Trinity as God entire." Related: Autotheist; autotheistic.
