late 14c., "unexpected attack or capture," from Middle French surprise "a taking unawares," from noun use of past participle of Old French surprendre "to overtake," from sur- "over" (see sur-) + prendre "to take," from Latin prendere, contracted from prehendere "to grasp, seize" (see prehensile). Meaning "something unexpected" first recorded 1590s, that of "feeling caused by something unexpected" is c.1600. Meaning "fancy dish" is attested from 1708.
Surprise party originally was a military detachment (1841); festive sense is attested from 1858.