In Brazil, it is a common practice to add “-inho” or “-ao” to a name; “-inho” means “little” while “-ao” means “big.” It is similar to the way we add “senior” and “junior” to differentiate people who bear identical names in this part of the world.
Legendary Brazilian striker Ronaldo Nazario used to be known as Ronaldinho (Little Ronaldo) to differentiate him from his older compatriot and teammate Ronaldo Rodrigues de Jesus who was dubbed Ronaldao (Big Ronaldo).
Also, during the Atlanta ’96 Olympics tournament, Ronaldo Nazario used the name “Ronaldinho” because there was another Ronaldo known as Ronaldo Guiaro, who was his senior in the team.
Years later, another Ronaldo came along named Ronaldo de Assis Moreira- and then became known as Ronaldinho- and the name has stuck with him till this day.
Some other famous Brazilian footballers who adopted this naming pattern include: Robinho (Robson de Souza), Cicinho (Cícero João de Cézare) and Edinho (Edson Cholbi do Nascimento).
Source: The Guardian