Simplify the following text for a Grade 4 native English-speaking person.
Original: Among the Nilotic Kavirondo married men who are fathers wore a small piece of goat-skin ( Sembe ) , which though practically useless as a covering was worn according to ethnic etiquette .
Simplified: The men of the Nilotic Kavirondo start to wear a small piece of goat-skin on their penis when they become fathers . This is called Sembe .