elbow grease vs exertion

elbow grease and exertion both are nouns.

Word	Noun	Adjective	Verb	Adverb
elbow grease	Yes	No	No	No
exertion	Yes	No	No	No

As nouns, elbow grease and exertion are synonyms defined as:

Other synonyms of elbow grease include effort, sweat, travail.

elbow grease (noun)	exertion (noun)
use of physical or mental energy; hard work	use of physical or mental energy; hard work