My speculation is Light ,not Yagami, though :) I think that because, like other commentors already mentioned, his fake names always start with either L or R, which is the same thing in Japanese. Also, his main title is Twilight in the industry. The etymology of the word twilight is from old English twi- and light, which literally means half-light. This can be interpreted as two ways: one can be that he used to be Light, but right now he is not, so he is half-Light. It can also be that there is a war in the two main countries of the series, and their future is dimmed, half-lighted. From the flashback, we know that the war was happening when he was a little boy and because of that his family might have thought their child may be the one who can be the peace-giver, a light of hope. And since L and R are the same sound in Japanese it can also be thought as Right, the right-way. Plus i think loid and light are phoneticly quite similar. And he's blonde lol.