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").

The general meaning "something unexpected, that which causes a feeling of surprise" is recorded by 1590s, that of "feeling of astonishment caused by something unexpected" is c. 1600, as in taken by surprise (1690s).

We are surprised at a thing because we did not expect it, astonished because of its remarkableness in some respect, amazed because we cannot understand how it came to pass, astounded so that we do not know what to think or do. [Century Dictionary]

Surprise party originally was a stealth military detachment (1826); festive sense in reference to a group assembling by arrangement at the house of an unsuspecting common friend and bringing the makings of a supper, 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. A surprise cup was a trick cup (one with a false bottom or some other device).

The 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]

also formerly surprize, late 14c., surprisen, "overcome, overpower" (in reference to emotions, a sense now obsolete), from the noun or from Anglo-French surprise, fem. past participle of Old French surprendre (see surprise (n.), and compare supprise).

The military sense of "attack without warning" is by 1540s; the general sense of "come upon unexpectedly" is from 1590s; that of "strike with sudden astonishment" is 1650s.