kingpin vs swivel pin

kingpin and swivel pin both are nouns.

Word	Noun	Adjective	Verb	Adverb
kingpin	Yes	No	No	No
swivel pin	Yes	No	No	No

As nouns, kingpin and swivel pin are synonyms defined as:

kingpin and swivel pin: bolt that provides a steering joint in a motor vehicle

Other synonyms of kingpin include kingbolt.

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