There are various myths regarding the naming of Chainpur. According to the legend, its name was Chandrapur because it was a beautiful place like the moon, later it was corrupted to become Chainpur. According to another statement, after the invasion of Vijayapur by the Makwarane Sen kings, the name of this place came to be Serpu and later became Chainpur after being corrupted from it. According to another account, when Sikkim was dominated by Bhote and Lepchas, the name of this place was Gola Bazar which means trading centre. They used to carry the dead body to a slightly higher place and bury it. Their opponents started calling this place Chihanpur instead of Gola Bazar on the basis that it was the place where the graves of Lepcha and Bhote were taken and later the name of Basai became Chainpur. According to another statement, it is a very suitable place to live due to having a very favorable climate, beautiful scenery, etc.