Dictionary:

sachem

  (sā'chəm)

1. 1. A chief of a Native American tribe or confederation, especially an Algonquian chief.
   2. A member of the ruling council of the Iroquois confederacy.
2. A high official of the Tammany Society, a political organization in New York City.

[Of Massachusett origin.]

Sachem, a term drawn from Algonkin speakers of the Northeast. Although English colonists in New England applied the term to most Indian leaders, the term truly applied to hereditary civil leaders as opposed to war leaders who acquired their status through prowess in combat. Much of a sachem's leadership depended on establishing consensus among the members of his village. Most sachems were men, but there are examples in New England history of women with the title. The term was adopted in the nineteenth century as a leadership title within the Tammany Hall political machine in New York City.

Bibliography

Salisbury, Neal. Manitou and Providence: Indians, Europeans, and the Making of New England, 1500–1643. New York: Oxford University Press, 1982.

The noun has 2 meanings:

Meaning #1: a political leader (especially of Tammany Hall)

Meaning #2: a chief of a North American tribe or confederation (especially an Algonquian chief)
  Synonym: sagamore