Sakata Gintoki (坂田銀時)
His name overall is a reference to the Japanese legend of Kintaro, which is about a child with massive strength during the Heian period(rather the later Edo period that Gintama takes place in). Kintaro became friends with the animals that lived on the mountain where he was raised, and was even capable of battling with them. After certain events, he became a samurai and eventually went under the name Sakata Kintoki (坂田公時). Sorachi-sensei, in one of the question corners explains this, and doesn't intend on making Gin-san a descendant of Kintaro.
There are random times when he is actually called Kintoki. Sakamoto mistakes Gintoki's name all the time, the OWee gaming console was unable to fit all the characters of his name (き/ki took one space while ぎ/gi took two), and the Gintoki in Gintama's alternate universe "Kintama" had golden hair and was called Kintoki.
