I've often wondered why certain products were named as they were. Here is my guess for EOS line:
Eos: Entertainment Operating System
Ion: An ion is an atom or molecule that has lost or gained an electrons. So it is the same type of thing with slightly different properties. So the Ion runs the same OS as Eos, but has slightly differing properties.
Element: The most basic atomic structure that is still a pure substance. Element is the most basic console of the Eos line distilled down to the essentials.
Gio: Play on the way an LD will some times refer to the <GO> key without saying the word "go". Also implies that this console is more intended as a road console.
Eos Ti: Titanium is a strong light metal. So it is a stronger, reinforced version of the Eos.
So, marketing folks, how did I do?
-Steve