Boo,
Moon,
Moonlight,
Moony,
Clay,
Circle Guard,
Circle,
Mumma,
Papa,
Mum,

And with her being called Boo, she has a twin with the matching name, her twin is Ran. Her opposite, but it's not twin as in twin sister or brother, it's as in twin lover, so her lover designed Ran and is now sometimes known as Ran, Boo's lover,