Siddhattha Gotama was the Buddha’s personal name. His given name, Siddhattha, means ‘He Who Attains His Goal’ and Gotama was his family name. After his enlightenment Siddhattha was usually called by his disciples Buddha or Tathàgata and was known as Sàkyamuni, or ‘the monk Gotama’ by others.
See also: Buddha
The Historical Buddha, H.W.Schumann, 1989.