It can mean "moon" from the Japanese translation but according to Korean, it Yuna (or at least
Yun, to my knowledge) can be translated to "allow, consent".
Kim Yuna's hangul name (according to wikipedia) would actually be translated to
Kim Yeon-a but is written as
Kim Yuna due to a mistake.
Yeona is usually meant as beautiful child so..I guess beautiful child is the usual translation