Meaning

noun a person who enjoys telling or playing jokes

noun a person who does something thoughtless or annoying

noun an inconspicuous clause in a document or bill that affects its meaning in a way that is not immediately apparent

originFrom joke + -er, but in the sense of a playing card possibly by alteration of German Jucker, also the origin of the name of the card game euchre.

Etymology from Wiktionary, CC BY-SA 3.0