Not familiar with any community in Mason Co, Ky called Dietrich; however, long-closed now, the C.P. Dieterich & Bro. greenhouses & nurseries were a Maysville fixture for years. This was located just east of Maysville along the C&O railroad, adjacent to the Maysville Cemetery. This firm, Dieterich & Bro., was started in the early 1860s, during or prior to the War Between the States. For many years, Dieterich's nurseries & greenhouses were the largest in the Commonwealth, and it's possible the nearby residents may have referred to this area as Dietrich (sic). Sadly, C. Perry Dieterich (both father and son) are deceased now. The rest of the family moved to the Lexington/Nicholasville KY area. Charlie, Billy, & some of their sisters may still be in central KY, but I haven't had any contact for decades.