At first, the characters were read in the Japanese way as 'Yamato,' and then read 'Jippon,' or 'Nippon,' which became established during around the Heian period, led up to the present day.
当初は国号の通り「ヤマト」と読まれていたが、やがて「ジッポン」「ニッポン」などと音読されるようになり、それが平安時代頃に定着し、現在へ至ったとされる。