kingpin vs headpin

kingpin and headpin both are nouns.

Word	Noun	Adjective	Verb	Adverb
kingpin	Yes	No	No	No
headpin	Yes	No	No	No

As nouns, kingpin and headpin are synonyms defined as:

kingpin and headpin: the front bowling pin in the triangular arrangement of ten pins

kingpin (noun)	headpin (noun)
bolt that provides a steering joint in a motor vehicle	the front bowling pin in the triangular arrangement of ten pins
the front bowling pin in the triangular arrangement of ten pins
the most important person in a group or undertaking