Kao is assumed to be generated in 8th century at Tang Dynasty, China. In Japan, Kao is used from mid of 10th century.

Before Kao became popular, the name signature was used, however, to distinguish the signatures it had been adopt an element of designing. It designed from a part of the name.

Kao, born from aristocrat society had outbreak to the samurai society. After Kamakura period (1185~1333), documents issued by samurais increased, therefore, samurais’ Kao had gained its numbers too. By the age of civil war (1467~1573), styles of Kao diversified in many ways. Kao is not always made from its real name but designed from animal shape at this time of age.

Once get into the Edo period (1603~1868), a stamp that has Kao pattern gained popularity. Kao and the stamp were used at same situation, however, the stamp became lot more popular because of its easiness and Kao loses its popularity.

By Dajokan Fukoku-rei, or Decrees of the Cabinet, on 1873 October 1st, a official documents without registered seal are no more accepted. It does not directly means that Kao has prohibited, but Kao loses its appearance and seals have used more after this Act. The Act abolished afterward, Kao never gained its popularity as it has before. In addition, from the age of Meiji, Kao has used as a ministers signature at cabinet meeting, and still, this custom remains. You can see past prime ministers Kao at Prime Minister’s office official website.

http://www.kantei.go.jp/jp/rekidai/souri/index.html

Kao in the world

The culture of Chinese Kao has continued through Ming Dynasty or Qing Dynasty, but then became unpopular.

We can see very close to Kao on all over the world. For instance, “Tughra” in Islam culture is Arabic signature that Sultan or person in power in Ottoman Turks used. Its shape and word are different by the person.