According to <a href="https://historiansabode.blogspot.com/2011/03/what-is-origin-of-saying-six-feet-under.html">What is the origin of the saying "six feet under"</a>, <bq>The phrase "6 feet under" originated in London, England in 1665. <b>It came about as London was being ravaged by the Bubonic Plague.</b> [...] The mayor of London at the time issued a decree that all plague deaths had to be buried at least "6 feet under" to help halt the spread of infection.</bq> 355 years later, another plague has made the expression "six feet" <i>au courant</i>, at least in those countries still using the imperial system of measurement. Even the nerdy <a href="https://xkcd.com/2286/" author="Randall Munroe" source="XKCD">6-Foot Zone</a> does it. <img src="https://imgs.xkcd.com/comics/6_foot_zone.png">