There were conflicting stories on how Atimonan got its name. Some concluded that the name of the town originated from a tree known as ATIMON alleged to have been prevalent in the area and had reportedly served many uses to the residents. But no account validated the existence of these trees.
Others say it was derived from the common saying ATIN MUNA, a guiding principle signifying a strong feeling of unity among the natives in their fight against Moro pirates and foreign invaders that disrupted their peaceful living.
But the most popular and accepted version was, it originated from the name of its founder, SIMEONA MANGABA, known to her town mates as ATE MONANG. She was a woman reputed to be of unquestionable leadership. The town folks regarded her as their adopted parent, leader and protector.
Based from the written account of Jesus Olega, a local historian, Atimonan was founded on FEBRUARY 4, 1608 by a group of families led by Simeona Mangaba at the place located near the mouth of a river, now Maling River. This group migrated from Kalilayan (now Unisan, Quezon) for fear of Moro attacks. Francisco Mangaba, the younger brother of Ate Monang was chosen the first captain of the town. However, since this place is open to Lamon Bay, they were once again bothered by Moro Pirates, that in 1609 they transferred to Palsabangon.
However, the group stayed in Palsabangon for only a year because the place abounds in wild crocodiles. In 1610, they decided to migrate in Kabuyaw, where they stayed for twenty four (24) years, but again migrated to another site called Minanukan (Brgy. Talaba, Atimonan) for unaccounted reason.
In 1635, they again relocated the town in a place called Bisita (Brgy. Concepcion, Plaridel, Quezon), but some families separated from the majority and settled in Yawe, now San Isidro, a barrio in Padre Burgos, Quezon.
The next year, 1636, Ate Monang, Fray Geronimo De Jesus, a Spanish friar and Captain Pablo Garcia, the town's chieftain, tried to reunite the people and convinced them to return to the place where it was first founded, the place was still known to this day as Bagumbayan.
Today, ATIMONAN is a fast growing town known for its beautiful scenery, beaches, historical landmarks, warm and peace-loving people.