ichou,s origin

Now, there are beautiful colored leaves in my university.Especially, avenue of ginkgo is very beautiful.Ginkgo is “ichou”.Do you know ichou,s origin? There is orogin of ichou,pronunciation in China.In the days of a thing of Sung,they pronounce Ya-chao about duck,s legs.And, the southern part in Chinese pronounce I-chao about this.It is considerd to have reached Japan in the Kamakura era.In other words the name of the ginkgo comes from the foot of the duck with the web.