Jaywalker is a popular pejorative that also enjoys a legal definition. Most of us have heard the term, but we are unaware of its history or even what “jay” means.
The blog Grammarphobia has an article ‘on jays and jaywalkers’ which answers the questions you may have never thought to ask.
The word “jay” in this context does not refer to the bird, but rather an old-timey slang word for “a stupid, gullible, or contemptible fellow.” Anyone stupid enough to walk on the wrong side of the road was ridiculed as a jay.
Interestingly, the term “jaydriver” appeared around the same time as “jaywalker.” Drivers would also find themselves confused as to which side of the road they should use in those early days of auto transportation.
The Grammarphobia article notes this observation:
Merriam-Webster adds that it’s “unclear why jaywalker shifted its meaning and survived for more than a hundred years now, while jay-driver languishes in obscurity.”
I assume that “jaywalker” would have languished in the past as well had it not become enshrined in law books. Either way, we still hold contempt for people who dangerously walk across the street, but consider dangerous driving to be just a mistake anyone could make.