Regarding History: > The earliest such proposal I could find was this one from 2009. (https://lists.w3.org/Archives/Public/www-style/2009Apr/0225.html) This sounded familiar (as in I thought I had proposed something similar a while ago), and it turns out I had proposed exactly a "tooltip pseudo-element" nine years earlier 🙈😭 https://lists.w3.org/Archives/Public/www-style/2000Apr/0014.html Note that the year 2000 was before the WG switched to the "::" prefix for pseudo-element selectors, so all pseudo-elements and pseudo-classes used the single ":" prefix.

Regarding History:
> The earliest such proposal I could find was this one from 2009. (https://lists.w3.org/Archives/Public/www-style/2009Apr/0225.html)

This sounded familiar (as in I thought I had proposed something similar a while ago), and it turns out I had proposed exactly a "tooltip pseudo-element" nine years earlier 🙈😭

https://lists.w3.org/Archives/Public/www-style/2000Apr/0014.html

Note that the year 2000 was before the WG switched to the "::" prefix for pseudo-element selectors, so all pseudo-elements and pseudo-classes used the single ":" prefix.