"look down upon, scorn, disdain, treat with contempt," c. 1300, despisen, from Old French despis-, present-participle stem of despire "to despise," from Latin despicere "look down on, scorn," from de- "down" (see de-) + spicere/specere "to look at" (from PIE root *spek- "to observe"). Related: Despised; despising.
To despise is to look down upon with strong contempt from a superior position of some sort. To scorn is to have an extreme and passionate contempt for. To disdain is to have a high-minded abhorrence of, or a proud and haughty contempt of. [Century Dictionary]