I am thinking the first time he is tired of getting shot down or laughed at so one day he just kind of gets bold and just goes for it with a group of girls saying flat out he has a small penis. The girls naturally want to know how small are we talking. Afterward its a bit of word of mouth.
Small-dick-guy (SDG) is a college sophomore. He has a female friend in a sorority, they are good friends, but never together. She knows about his short-coming because he told her.
At the sorority hazing, she invites him, and orders all the pledges to give up her anal cherry to SDG. He gets a following, and he is soon in demand across campus for other pledge hazings.