I am going to take a stab at this.
Xeos_ has it beginnings in the mind of a young boy who as an only child had to learn to entertain himself. Naturally being drawn to Sci-Fi, especially falling in love with Stargate the TV series, he began to write fiction and imagine himself as a part of that universe. He struggled to come up with new names for starships after all the cool ones had either been taken or were not unique in this boy's mind.
Then while coming up with things to name a starship, he thought huzzah: the XENON! But then he realized that seemed familiar, and it hit him: IT WAS AN ELEMENT. But the X sound stayed with him.
Years later when the boy became a teenager and discovered this new technology named Twitter, it asked him for a username. The teen tried his name, but alas some other apparently more popular "Jesus" had taken his name.
"Blast!" the teenager yelled. How else was he to follow his favorite authors, directors, actors, and musicians?? The teen thought long and hard about what he wanted as a Twitter name, then it struck him X something! But he remembered he couldn't be the element, so again he thought hard and with a stroke of blind luck he typed in Eos the greek goddess of dawn after the X. And to ensure that he would be a unique xeos so that the page would not say this username has been taken, he hit one of his favorite keys the underscore. And on that day a new username was born that this teen would systematically use as his online identity to this day.