Viktor, Cedric, Fleur and Harry all caught in the act while unwinding some stress during the Twi-Wizard Tournament (abrosiis)
Ukemi = bottom: the verb ukeru means to "take, receive, accept," thus uke (receiving) mi (body, party) means "one who receives," or, "a bottom." Neko = bottom: neko literally means "cat". It has exactly the same meaning as ukemi, but in a slangier way.