"Pupendo" is a childish game, usually played by boys or sometimes men, who allow their mates to throw a coin on their belly with full strength. The result is visible in the photo.
<a href="//commons.wikimedia.org/wiki/User:Frettie" title="User:Frettie">Frettie</a>
CC BY 3.0
<span class="int-own-work" lang="en">Own work</span>