1660s, "dazzling," present-participle adjective from stun (v.). Popularized for "splendid, excellent" c. 1849. Related: Stunningly.
Entries linking to stunning
stun v.
early 14c., "to daze or render unconscious" (from a blow, powerful emotion, etc.), probably a shortening of Old French estoner "to stun" (see astonish). Related: Stunned; stunning.