The English word Japan comes from the ‘Wu’ dialect of Chinese via Portuguese word ‘Cipangu’. The first recorded example in English belongs to the 16th century. Japan was then spelled ‘Giapan’. Later the name got corrupted and changed into its modern version ‘Japan.’
The Japanese themselves call their country ‘Nippon’ or ‘Nihon’, which can be translated as ‘the land of the rising sun’. Nippon is more formal and it used for official purposes. For example, the official name of Japan’s international public broadcaster, Japan Broadcasting Cooperation is Nippon Hoso Kyokai and it is abbreviated as NHK, or NHK-World in English.
The name ‘Nippon’ first appeared in the 7th century, when the then emperor ordered the name of the country to be changed. The earlier name was Woguo and it is said that the emperor didn’t like that name.