Yeah, I got wooshed on that one, too. If I had to guess though, I'd say it alludes to the Naturalist movement, wherein she uses the term "floppy" to represent the trapped emotions that lie within Tenzen himself, where though he knows not why he attacks the group, within he knows he must. So he flops between one extreme to the other, unsure of which is his true destiny.
Or it could be because he kinda looks like a bunny.