The term “weines,” or more commonly “wenis,” is not a real word and is not the name of the skin on the elbow. This myth is so popular however, that “wenis” verges on being a slang term. There is no specific term for that exact piece of skin; however it can be accurately described as “olecranon skin” or “skin of the olecranon.”
The olecranon is the name of the tip of the elbow; it is part of a bone in the forearm called the ulna. The ulna runs parallel to another bone, the radius. They extend from the wrist to the elbow where they are connected to the humerus which is the bone that runs from the elbow to the shoulder. The point at which all three bones (ulna, radius and humerus) meet is the olecranon process.
“Wenis” spelled backwards is “sinew.” “Sinew” is another word for “tendon.” And, there is indeed a tendon in the elbow. So, the skin isn’t called wenis, but there is a backwards wenis, so to speak, below that skin.