Only one word in box B refers to one word in box A. Which word we are looking for?

Interesting fact:

Have you been paying close attention to all the creatures mentioned in the Harry Potter universe? Kappas are terrifying things from Japanese folklore that feed on humans and derive strength from water held in the hollow of their heads. The only way to protect oneself from an attack is to hurl a cucumber with your name engraved on it. Luckily we all carry one of those around at all times.