customs vs ship money

customs and ship money both are nouns.

Word	Noun	Adjective	Verb	Adverb
customs	Yes	No	No	No
ship money	Yes	No	No	No

As nouns, ship money is a hyponym of customs; that is, ship money is a word with a more specific, narrower meaning than customs:

customs: money collected under a tariff
ship money: an impost levied in England to provide money for ships for national defense

customs (noun)	ship money (noun)
money collected under a tariff	an impost levied in England to provide money for ships for national defense