1793, "to corrupt or undermine the morals of," from French démoraliser, from de- "remove" (see de-) + morale (see morale). Said to be a coinage of the French Revolution. Sense of "lower the morale of, deprive of courage and confidence" (originally especially in reference to armed forces) is attested by 1842; in colloquial use, "to throw into confusion generally." Also demoralise. Related: Demoralized; demoralizing; demoralization.