Let's continue the spoiler trend!
EDIT: screw the spoiler trend. Everyone below me ignored it.
Solgaleo and Lunaala, eh? Aside from the obvious associations with the sun and the moon, the first things that stuck out to me in each of them were:
SolgaLEO: Leo implying a lion. Lions are associated with royalty, and the sun is very much considered with a certain regal sense of importance. I understand these are Japanese names, and I don't know if it quite translates this way, though. Anyone able to clarify?
LunAAla: I'm certainly less confident about this one, but the double A made me immediately think of sheep ('baa'). Wouldn't be the first time we've had a sheep mon with two consecutive A's in the name (Flaaffy anyone?). While I'm not sure how sheep tie in directly with the moon, the moon is associated with night, and we're supposed to count sheep at night to get to sleep. I, for one, am perfectly happy to get Moon on the grounds of the Moon-Sheep god.