According to Cow Mow, one of the oldest Chinese traders associated with the East India Company,
“Tea has been known from time immemorial. There is a mountain called Singlo mountain. Tea was originally produced here, so that the tea planted in other places was called Singlo Tea, also hill tea. That which is called Yuen or garden tea is the Singlo tea planted in gardens. This custom prevailed so far back as the dynasty of Sung (960-1278). Hyson tea was formerly called garden tea, and was first cultivated in the towns of Hieu Ning and Moo Yuen. In the reign of Can Hee (1661-1722) a man used for his sign the two characters Hee Chun, or Hyson. Shortly after all garden tea was called Hee Chun of Hyson.
Following the rolling of the green tea, the leaves are hand sorted by women with the best leaves set aside as Singlo skins. The second grade being Singlo. The large closely twisted leaves form the Hyson teas. The large open and knobby leaves form the superior Hyson skin teas.”