Consul Butterfield used the accepted language of his time regarding
Native Americans, commonly referring to them as "savages."
The best book on Girty (and his brothers) remains Consul Willshire Butterfield, History of the Girtys (1890), although it is sometimes difficult to read. A newer work is Thomas Boyd, Simon Girty: The White Savage (1928). Richard Elwell Banta, The Ohio (1949), has a solid biographical sketch of Girty. For general historical background see Dale Van Every, A Company of Heroes: The American Frontier, 1775-1783 (1962).
Additional Biography Sources
Truman, Timothy, Wilderness: the true story of Simon Girty, the renegade, Lancaster, Pa.: 4 Winds Pub. Group, 1989.