Sei is of Japanese origin, meaning 'pure' or 'clear'. It's composed of two characters: 'sei', which means 'pure', and 'ha', meaning 'river'. Thus, Sei can also convey the idea of a clear river. The name has been popularized by several notable figures, such as the Japanese author Mori Ogai's pen name, Natsume Soseki, who used 'Sei' in his full name. However, it remains relatively uncommon outside Japan.
"Sei was given to 7 babies in 2007."