What does Yakyuken mean? And what does RSP have to do with baseball?

Yakyuken literally means "baseball fist", and is another name for Jankenpon or Rock-scissors-paper based on the chant that is sometimes sung in Japanese matches where clothing loss is involved, although sometimes the game is simply referred to as Janken. The name "Yakyuken" is taken from the chant, in that the Japanese word for Baseball is "Yakyuu". The chant, whose lyrics are (as near as I can figure it):

Yakyuu suru nara
Kouiu guai ni shiyashanse
Nagetara, kou utte
Uttanara, kou ukete
Rannaa ni nattara
Essassa
Aauto! Seifu!
Yo-yoi-no-yoi!

loosely translated, means, "If you play baseball, it should be played like this. Throw like this, it's a strike! If it's hit, catch like this! When you're the runner, hustle! Hustle! Out! Safe! Yo-yoi-no-yoi!"*. Only a few yakyuken games I've found actually use this chant in whole or part, but in sessions outside computer games in Japan it seems to be used commonly along with a dance, as pictured in The Yakyuken Special.

* - I realize this is probably not even close.