In early 1900s America, “jay” was a slang term used to describe a naïve or foolish person. Thus, when such a pedestrian decided to ignore traffic signals and street signs, he or she was referred to as a “jaywalker.”
DID YOU KNOW? Marlon Brando hated memorizing lines so much that he posted cue cards everywhere to help him get through scenes.
He even asked for lines to be written on an actress's posterior. (That request was denied.)