Also, tickled to death. Delighted, as in I was tickled pink when I got his autograph, or His parents were tickled to death when he decided to marry her. The first term, first recorded in 1922, alludes to one's face turning pink with laughter when one is being tickled. The variant, clearly a hyperbole, dates from about 1800.
Dictionary.com presents 366 FAQs, incorporating some of the frequently asked questions from the past with newer queries.