What is Chinto?
This kata is said to have been taught to Matsumura Sokon by a Chinese named Chinto, but this legend cannot be corroborated. According to a 1914 newspaper article by Funakoshi Gichin (1867-1957, founder of Shotokan karatedo), based upon the talks of his teacher Asato Anko (1827-1906), student of Matsumura Sokon):
"Those who received instruction from a castaway from Annan in Fuzhou, include: Gusukuma and Kanagusuku (Chinto), Matsumura and Oyadomari (Chinte), Yamasato (Jiin) and Nakasato (Jitte) all of Tomari, who learned the kata separately. The reason being that their teacher was in a hurry to return to his home country." (sic, Shoto, 1914).
It is believed by this author that the "Matsumura" in the above excerpt is a misspelling of Matsumora Kosaku, of Tomari. The fact that Matsumora Kosaku, is evidence that Matsumora may have also been taught this kata as well (Kinjo, 1999).
Now, what exactly is Chinto? There appears a form called Chen Tou in Mandarin Chinese (Jpn. Chinto, lit. Sinking the Head) in Wu Zho Quan (a.k.a. Ngo Cho Kuen, Five Ancestors Fist), which was a style popular in the Quanzhou and Shamen (Amoy) districts of Fujian (Kinjo, 1999). Chen Tou refers to sinking the boy and protecting the head. In the Okinawan Chinto kata, this is the first technique, but in the Five Ancestors Fist it is the last (Kinjo, 1999). However, this being said, this author has yet to see the Chen Tou form to make a comparative analysis. It is, however, worthy of further investigation.
There are 3 distinct "families" of Chinto in modern Okinawan karate: Matsumura/Itosu lineage (performed front to back), Matsumora Kosaku lineage (performed side to side), and Kyan Chotoku lineage (performed on a 45 degree angle). Looking at technical content, we can see that the Matsumora and Kyan versions are nearly identical, which is only natural since Kyan learned this from Matsumora.
*from The Kata of Okinawa Isshinryu Karate-do: An Informal Discussion on their Possible Origins by Joe Swift