HTML does have the <ABBR> tag. I use it all the time on my blog any time I use an acronym [1]. At least Firefox and Safari will display the title attribute as a tool tip, so hovering over the following HTML: "<abbr title="Border Gateway Protocol">BGP</abbr>" on those browsers will show "Border Gateway Protocol". I'm sad that it's not used more often.

[1] An example: http://boston.conman.org/2022/02/16.1