Emperors' names traditionally end with the character "hito," meaning the highest moral standard (virtue), while names for royal women end in "ko", meaning noblewoman.
Names ending in "hito" are highly unusual for commoners and while "ko" was once a popular name ending for girls, it is increasingly rare for new babies.
The six-day-old Japanese heir to the throne -- who, we're sad to say, we can't show here because he's being hidden away from photographers, Suri-Cruise style -- is no longer nameless. His parents have decided to call him Hisahito, or "serene one," reports the Times of London.
The baby will be given a name composed of two Chinese characters. If it is a boy, the name will almost certainly end with the character "hito". If the infant is a girl, the second character will likely be "ko".
"'Hito' means the highest moral standard. What a leader should aim to attain ... And 'ko' means a noble woman," said Yasuo Ohara, a classics professor at Kokugakuin University.
The imperial family has stuck to this rule for centuries and an emperor whose name ends in "hito" can be found as far back as the ninth century.