The belly button is part of our normal anatomy. This is a constant reminder that we were once connected to our mothers inside the womb and it seems unlikely that one will fear it but those who fear belly buttons are said to have omphalophobia.
People could have been triggered by false beliefs such as playing with one’s belly button too much and puncturing it accidentally can kill you instantly. This has been passed on in some cultures from the elderly and they forbid people to clean their belly button. Others might also fear the belly button because of the deformity or dimple it creates in the abdominal wall. For others, they might have a friend who had a belly ring which got infected and nearly died because of it.
People with this fear will try their best not to manipulate their belly buttons. They will not touch it when taking a bath and some may go to the extent of putting a cover or plaster over their belly buttons to protect it. They will not go to places where they would expect to see belly buttons such as the beach where most people are in bathing suits with exposed navels.
Treatment includes psychotherapy.