There never was a Nipmuc tribe as such. Nipmuc is a geographical classification given to the native peoples who lived in central Massachusetts and the adjoining parts of southern New England. They lived in independent bands and villages, some of which at different times were allied with, or subject to, the powerful native confederacies which surrounded them. Massomuck, Monashackotoog, and Quinnebaug were Nipmuck, but they were subject to the Pequot before 1637.
Nipmuc History History of the Nipmuc by Lee Sultzman