Kappa translates to river child. (L) Kokeshi Kappa with river water kept in a container on his side. (R) Kappa Mailer, you can see the lily pad like bowl on his head and the bottom screw cap which comes off to allow for a short message to be sent hidden inside it.

Kappa are legendary creatures in Japan, and even regarded to as a water deity. They are described as having reptilian skin in tones of yellow, blue or green and are the height of a child. Kappa's are best known for their mischievous nature. It is believed that Kappa folklore was a form of warning children of the dangers of playing in bodies of water. Children are often scared as they hear the tales of the, web feet, creature that comes out of the ponds, rivers and lakes to lure them in and drown them. Though Kappa's are not all bad, they are extremely polite and if you ever need to escape from an encounter with a mean kappa you simply need bow, they will return the bow and lose the water contained in the, lily top like, bowl on their head rendering them powerless and unable to move. If you had mercy on the poor mischievous Kappa you would refill the bowl with water from the river they were in and the Kappa would serve you and your family for all eternity.

Further Reading: On Mark Productions - Kappa Wikipedia -  Kappa