Translation: The Japanese katakana "pegasasu" is a pretty easy guess as to it's meaning, especially with the visuals of the winged horse. It's Pegasus. I am concentrating on the Japanese katakana "eriosu" for this name section. So, here we go....

The katakana for the this name is "eriosu" which is the Japanese approximation of the name "Helios" from Greek mythology. The name Helios is much more fitting than "Elios" which is not even a real word. The names in the Sailormoon series are usually either mineral/gemstone based or mythological based, though other themes have been developed (flowers, sweets, etc).

Helios was the sun god of Greek mythology (and brother to Selene and Eos). The theming for this character falls with Prince Endymion's theme. This theme would be associations with gold and the sun which compliments Princess Serenity's silver theme. Mamoru has been said to be protected by the sun. Then there is also the Golden Crystal and the Golden Kingdom.

Ian-san has come up with an article that gives the best explaination on why the name is Helios and not Elios. Please click here to read it.