The feeling caused by something unexpected.
The feeling caused by something unexpected — the broad base term, freely positive, negative, or neutral.
The generic reaction to the unexpected, and the only member that is freely bidirectional in valence (“a pleasant surprise,” an unwelcome one, or a flat one). It stresses being unexpected, not necessarily unusual, incomprehensible, or admirable. The others intensify or color it: astonishment adds remarkableness and being stunned; amazement adds bewildered admiration; wonder adds reverence and curiosity; shock adds a distressing jolt; dismay adds discouragement.
From Old French surprise “a taking unawares,” from sorprendre “to overtake, seize” (sur- “over” + prendre “to take,” from Latin prehendere “to grasp”). The literal sense is “an overtaking.”
Originally concrete and military: “unexpected attack or capture” (late 14c.). The emotional senses followed — “something unexpected” by the 1590s, the feeling by c. 1600. The military sense survives but is now secondary. No reliable recent-generation shift.