Mehmet was an ancient prophet venerated by the Sathuli. His teachings were central to the Sathuli religion. It was not uncommon for followers to swear by his soul, and they would follow any mention of his name with the prayer "Blessed be His Name".
Mehmet is presumably based on the Islamic prophet Muhammad, which follows the general Arab / Middle Eastern inspiration of the Sathuli. "Mehmet" is in fact a common Turkish form of the Arabic name Muḥammad.