surprise n.

also formerly surprize, late 14c., "unexpected attack or capture," from Old French surprise "a taking unawares" (13c.), from noun use of past participle of Old French sorprendre "to overtake, seize, invade" (12c.), from sur- "over" (see sur- (1)) + prendre "to take," from Latin prendere, contracted from prehendere "to grasp, seize" (from prae- "before," see pre-, + -hendere, from PIE root *ghend- "to seize, take").

Meaning "something unexpected" is recorded by 1590s, that of "feeling of astonishment caused by something unexpected" is c. 1600. Meaning "fancy dish" is attested from 1708.

A Surprize is ... a dish ... which promising little from its first appearance, when open abounds with all sorts of variety. [W. King, "Cookery," 1708]

Surprise party originally was a stealth military detachment (1826); festive sense is attested by 1857; according to Thornton's "American Glossary," originally a gathering of members of a congregation at the house of their preacher "with the ostensible purpose of contributing provisions, &c., for his support," and sometimes called a donation party. Phrase taken by surprise is attested from 1690s.

also formerly surprize, late 14c., "overcome, overpower" (of emotions), from the noun or from Anglo-French surprise, fem. past participle of Old French surprendre (see surprise (n.)). Meaning "come upon unexpectedly" is from 1590s; that of "strike with astonishment" is 1650s.