trembling vs shakiness

trembling and shakiness both are nouns.

Word	Noun	Adjective	Verb	Adverb
trembling	Yes	Yes	No	No
shakiness	Yes	No	No	No

As nouns, trembling and shakiness are synonyms defined as:

Other synonyms of trembling include palpitation, quiver, quivering, shaking, vibration.

trembling (noun)	shakiness (noun)
a shaky motion	the quality of being unstable and insecure
	a shaky motion

trembling (adjective)	shakiness (adjective)
vibrating slightly and irregularly; as e.g. with fear or cold or like the leaves of an aspen in a breeze