For which aspects of Brando's personality is he regularly teased, according to the narrator?

The narrator provides a clue about the source of Brando's rage and burning need to prove his masculinity in Chapter VI. It is said that for years now, Brando has been the subject of ridicule by his friends and other boys his age. They mercilessly tease him about his name and his allegedly small penis. In addition, before he lost his virginity, his condition inspired great hilarity among his group of friends.