sachem vs Indian chieftain

sachem and Indian chieftain both are nouns.

Word	Noun	Adjective	Verb	Adverb
sachem	Yes	No	No	No
Indian chieftain	Yes	No	No	No

As nouns, Indian chieftain is a hypernym of sachem; that is, Indian chieftain is a word with a broader meaning than sachem:

sachem: a chief of a North American tribe or confederation (especially an Algonquian chief)
Indian chieftain: the leader of a group of Native Americans

Other hypernyms of sachem include Indian chief.

sachem (noun)	Indian chieftain (noun)
a chief of a North American tribe or confederation (especially an Algonquian chief)	the leader of a group of Native Americans
a political leader (especially of Tammany Hall)