[I don't think Childe has any reason to know about Genshin constellations so he can't say that that's what his is

But he shakes his head.]

Well, it's something I came up with when I was younger... I needed something that would do a lot of damage, but that would be creative and distracting enough to catch people off-guard, and my home village is next to the ocean, so...

[A shrug! It made sense.]