Sometimes it pays to be over 40… :D :D :D
The first suitcase-sized PCs were called “portables”. They had CRTs (about 9”) and require to be plugged it. More than portables, they were luggables.
Next generation were the first PCs with LCD screens, the first models still not running on batteries, but small and “light” enough that you could operate in your lap. That’s were the term “lap-top computer” comes from.
When portables became smaller, some manufacturers used the slogan “small as a notebook, it will fit in your briefcase”. Standard industry size for “notebook-sized” computers became the proverbial 8.5"x 11”, so you could still carry them in your briefcase. Samsonite loved the idea!!!
So, that’s the story as I remember it. Today, notebook, laptop, portable, etc it all refers to computers you can carry with you.
Best,
Marcelo