There are a few different versions of how Greentown received its name. One of the more obvious versions would be that Greentown was an area of luscious green grass. Another version deals with the fact that before the town was incorporated that land was a part of a former township named Green Township. Green Township formed into both Liberty and Union Townships in 1860, and so even though Greentown wasn't incorporated until the 1870s people were still living there when it was Green Township, and may have possibly all opted to preserve Green Township in some way by naming their town after it. One other version is based on the idea of Greentown being an Indian settlement named after a Native American chief called Green.