firewood vs backlog

firewood and backlog both are nouns.

Word	Noun	Adjective	Verb	Adverb
firewood	Yes	No	No	No
backlog	Yes	No	Yes	No

As nouns, backlog is a hyponym of firewood; that is, backlog is a word with a more specific, narrower meaning than firewood:

Other hyponyms of firewood include cordwood, brand, firebrand, pine knot.

firewood (noun)	backlog (noun)
wood used for fuel	an accumulation of jobs not done or materials not processed that are yet to be dealt with (especially unfilled customer orders for products or services)
	something kept back or saved for future use or a special purpose
	the large log at the back of a hearth fire

firewood (verb)	backlog (verb)
	accumulate and create a backlog