Every year on April Fools Day, you might find yourself the victim of a practical joke or two—getting drenched by the bucket of water over the door trick, maybe, or getting shocked by a buzzer when you shake someone's hand. But why are these jokes called practical?
Prop-based hijinks are called "practical jokes" because they require action—like slipping a Whoopee cushion onto someone’s chair—to be put into "practice." According to the Online Etymology Dictionary, the term was first used in 1804; before that, it was called a "handicraft joke," a term coined in 1741.
"Practical joke" also distinguishes such pranks from strictly verbal or intellectual jokes, such as the one about the Grecian Urn. (What's a Grecian Urn, you ask? Oh, about 250 drachmas an hour if he's union.)