Ball : nf arg. Ball skin! : Nothing or nothing at all.
“Ball” was a word of Gallic origin designating the husk of cereal grains. We find in Old French "ne value ball", that is to say to have no value. This expression which opposes the envelope of the grain to its content uses the symbolic distribution: exterior (without value) and interior (of great value), for example the gangue and the diamond, the bone and the substantive marrow, etc ... But the The word's scarcity in its envelope sense has transferred this pejorative value to phrases like "bullet skin" (ie: nothing).
From the Middle Ages, the word "pel" designated the skin of the male sex ("pel" in old Provencal, and the derivative "pelette", designated the foreskin). The expression "skin of my balls" being undoubtedly too light, it did not spread. "Peau de Node" has remained slang. "Zebi skin" (among the Zouaves around 1670) was more successful, even if the word "zébi", of Arab origin, was not always understood in France.