Origin: Old Norse, Japanese
Meaning: feminine form of Rune meaning “secret, lore”, which comes from Old Norse Rúni which comes from Norse element run.
I’ve also found the name listed as a Japanese female name, as well as a Bengali name, though I couldn’t find any meanings for them. The closest I could find a meaning was that maybe it’s a transliteration of Luna (moon) in Japanese since there seems to be some difficulty with the L/R pronouncation- but that’s all purely conjecture on my part.
According to http://nookofnames.com/2011/09/22/incan-inspiration/ , Runa is also a Quechuan word meaning “man, adult, mankind”