A wenis is a slang term used to describe the loose skin on the bottom of an elbow. According to Wiktionary, this “elbow definition” has not been made official and is just a slang term.
Definition-of.com describes the term wenis in several ways: the flap of skin on your elbow, the stretch skin on the bottom of your elbow, dry skin on your elbow and epidermis on your elbow.
Wenis was also the name of a Pharaoh of Ancient Egypt, and the last ruler of the fifth dynasty. It is believed that he reigned between 2375 BC and 2345 BC. The fifth dynasty came to an end when Wenis died.