What does your Username mean?

[luinil]

My name is the name of a star in Middle-Earth. It literally means "Blue Star." I created a character a while back (I think in City of Heroes) that I gave blue hair and called her Luinil. She was awesome! That is also a reason my avatar has blue hair, to match my name.

Edit: also the elvish phrase in my sig "Aina Elentari! Luin Elentir!" means 'Holy Elentari! Protect the Blue Star!' 

as a note, Elentari is another name for Arda, the Queen of Valinor, aka The West to the Elves. For more info read the Silmarillion.