I'm not sure of the history, but as far as I know, the Latin origin of the word Kira is based on light. Kira is also the Persian word for Sun, and a Russian form of Helen (light). The traditional Hindi meaning of Kira is ray.
Kira is also a masculine name in Japan, I believe, but don't know if it has meaning, or what it is.
I'd like to know, as well. I have been called by it for over three decades, thus far.