headman vs chieftain

headman and chieftain both are nouns.

Word	Noun	Adjective	Verb	Adverb
headman	Yes	No	No	No
chieftain	Yes	No	No	No

As nouns, headman and chieftain are synonyms defined as:

Other synonyms of headman include chief, tribal chief.

headman (noun)	chieftain (noun)
the head of a tribe or clan	the head of a tribe or clan
an executioner who beheads the condemned person	the leader of a group of people