Thonotosassa is a census-designated place in Hillsborough County, Florida, United States. The population was 15,238 at the 2020 census, up from 13,014 at the 2010 census. The name "Thonotosassa" comes from the Seminole-Creek words ronoto "flint" and sasv "some", meaning the place was a source of valuable flint. Following the establishment of F…Thonotosassa is a census-designated place in Hillsborough County, Florida, United States. The population was 15,238 at the 2020 census, up from 13,014 at the 2010 census. The name "Thonotosassa" comes from the Seminole-Creek words ronoto "flint" and sasv "some", meaning the place was a source of valuable flint. Following the establishment of Fort Brooke in 1824 in what is now Tampa, a road that ran northwest of Lake Thonotosassa was built between Fort Brooke and Fort King in Ocala. This road became known as the Fort King Road, which today is crossed in several locations by U.S. Route 301. Nevertheless, the presence of a Seminole village largely discouraged whites from moving into the area. After the Second Seminole War ended in 1842, whites began to settle.