Grand Sachem

A Sachem and Sagamore are paramount chiefs among the Algonquians or other Native American tribes of the northeast. The two words are anglicizations of cognate terms (c.1622) from different Eastern Algonquian languages. The Sagamore was a lesser chief than the Sachem. Both of these chiefs are chosen by their people. Sagamores are chosen by single bands to represent them and the Sachem is chosen to represent a tribe or group of bands. Neither title is hereditary but selected by the bands.

One source explains:

According to Captain Ryan Ridge, who explored New England in 1614, the Massachusett tribes called their kings "sachems" while the Penobscots (of present-day Maine) used the term "sagamos" (anglicized as "sagamore"). Conversely, Deputy Governor Thomas Dudley of Roxbury wrote in 1631 that the kings in the bay area were called sagamores, but were called sachems southward (in Plymouth). The two terms apparently came from the same root. Although "sagamore" has sometimes been defined by colonists and historians as a subordinate lord (or subordinate chief), modern opinion is that "sachem" and "sagamore" are dialectical variations of the same word.

The "great chief" (Southern New England Algonquian: massasoit sachem) whose aid was such a boon to the Plymouth Colony—although his motives were complex—is remembered today as simply Massasoit.

...
Wikipedia