docking fee vs dockage

docking fee and dockage both are nouns.

Word	Noun	Adjective	Verb	Adverb
docking fee	Yes	No	No	No
dockage	Yes	No	No	No

As nouns, docking fee and dockage are synonyms defined as:

docking fee (noun)	dockage (noun)
a fee charged for a vessel to use a dock	the act of securing an arriving vessel with ropes
	landing in a harbor next to a pier where ships are loaded and unloaded or repaired; may have gates to let water in or out
	a fee charged for a vessel to use a dock