Disclaimer: I don't own Harry Potter! J.K Rowling does.
"Daddy? Why is my middle name Luna?" Lily hopped up onto her father's lap and looked into his bottle-green eyes.
"Well, little Lily-flower," said Harry, brushing his daughter's fiery red Weasley hair from her eyes, "do you remember Lorcan and Lysander's mum?"
She wrinkled her nose. "Yes Daddy. Those boys were loud, but their mum was nice to me."
Harry smiled. "Well, that was Luna. She's an old friend of your mum's and mine and Aunt Hermione and Uncle Ron's."
"So I'm named after her?"
"Yes, but you're also named a bit after Teddy's father. Remember those stories about Remus Lupin? Well, Remus was a good friend, and his last name, Lupin, sounds a lot like 'Luna'. Luna means 'the moon' in Latin, and Remus was a werewolf, so it fits."
Lily gazed at her father. "Daddy, what's Latin?"
"It's an old language. People don't speak it anymore, but a lot of the words we use and the incantations for spells come from it."
"Oh. I see. I'm glad I'm named for your friends, Daddy." Lily snuggled closer and Harry hugged his youngest child.
"Me too, Lily-flower. Me too."