surprisal

The story

From surprise + -al. (information measure): Defined by Myron Tribus in the 1961 book Thermostatics and Thermodynamics.

First known use, by meaning

• 16th–19th c. A surprise attack or ambush; a sudden or unexpected assault.
• 17th c. A sudden coming-upon someone or something unexpectedly or unawares.
• 17th–19th c. A surprising event or occurrence.
• 17th–19th c. The feeling caused by being surprised; surprise, shock, amazement.