Indian chief vs Indian chieftain

Indian chief and Indian chieftain both are nouns.

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

As nouns, Indian chief and Indian chieftain are synonyms defined as:

Indian chief and Indian chieftain: the leader of a group of Native Americans

Indian chief (noun)	Indian chieftain (noun)
the leader of a group of Native Americans	the leader of a group of Native Americans