(( Ursus is a pun too. Cuz they have bear hands. Raine is a blue pun I guess. Don't know what Fran is a pun of since we haven't seen their monster quirk yet.))

Ursus - meaning brown bear, they’ve got bear fur + paws

Raine - means crown, also sounds like rain, loosely fits the swan theme too

Holl - “Holl”ow, Holl the Doll

Fran - Named after Francis Bacon, creator of the scientific method. Not a pun, sadly.