And there's actually a great article about this that was on HN in January -- the history of the term jaywalking:

https://www.vox.com/2015/1/15/7551873/jaywalking-history

Basically, automobiles were killing people in the streets, so manufacturers lobbied to get people off the streets and turn them into car-only thoroughfares, and invented a new term for their campaign -- jaywalking, where "jay" back then used to mean "hick" or someone from the country.