A static site still designates a site with no server-side processing, just serving of (static) content. As for it being plain HTML, no, it can be full of JS, vi

A static site still designates a site with no server-side processing, just serving of (static) content. As for it being plain HTML, no, it can be full of JS, videos, whatever, it's still static. I do remember a time when the expression "dynamic HTML" was popular to designate HTML+JS. Therefore, "static" may have been used in contrast to "dynamic" to designate plain HTML pages indeed. This is not the case now.