My favorite theory is that it's from plague times:<p>"People allowed to go out must bear with them a cane measuring six feet long. It is mandatory that people keep this distance from one another." via <a href="https://www.bbc.com/future/article/20210107-the-432-year-old-manual-on-social-distancing" rel="nofollow">https://www.bbc.com/future/article/20210107-the-432-year-old...</a>