A screen that directly projects onto the retina sounds like a great reason to call it a retinal display. So then Apple hijacking the term to mean high DPI... how does that fit in?
There's not that many results about this before Apple's announcement in 2010, many of them reporting on science and not general public media: https://www.google.com/search?q=retinal+display&sca_esv=3689... Clearly not something anyone really used for an actual (not research grade) display, especially not in the meaning of high DPI
This isn't an especially easily understood term: that it means "good" would have been obvious no matter what this premium brand came up with. The fact that it's from Apple makes you assume it's good. (And the screens are good)