surprise

1425–75; (noun) late Middle English < Anglo-French surpris( e), Middle French, past participle of surprendre, equivalent to sur- sur-¹ + pris (masculine), prise (feminine) < Latin prēnsus, -sa, equivalent to prēnd( ere), contracted variant of prehendere to take (see prehension) + -tus, -ta past participle suffix; (v.) late Middle English surprisen < Anglo-French surpris( e) (past participle), Middle French, as above

1. Surprise, astonish, amaze, astound mean to strike with wonder because of unexpectedness, strangeness, unusualness, etc. To surprise is to take unawares or to affect with wonder: surprised at receiving a telegram. To astonish is to strike with wonder by something unlooked for, startling, or seemingly inexplicable: astonished at someone's behavior. To amaze is to astonish so greatly as to disconcert or bewilder: amazed at such an evidence of stupidity. To astound is to so overwhelm with surprise that one is unable to think or act: astounded by the news.

The English noun surprise comes from late Middle English, from Anglo-French and Middle French surprise(e), a noun use of the past participle of surprendre “to seize, grasp,” literally, “to overtake," from the French prefix sur- “excessive, over-,” and the verb prendre “to take.”
The original 15th-century meaning of the English noun was “an unexpected or sudden attack without warning” (a surprise attack, therefore, was a redundancy). In the 19th century, the term surprise party came into use with two disparate senses: the earlier one was “a body of soldiers prepared to make a sudden, stealthy attack,” which held close to the original sense of surprise; the second, slightly later one was “a party or celebration planned for someone as a surprise,” which of course has survived as the meaning familiar to us today.