deathwatch vs book louse

deathwatch and book louse both are nouns.

Word	Noun	Adjective	Verb	Adverb
deathwatch	Yes	No	No	No
book louse	Yes	No	No	No

As nouns, deathwatch and book louse are synonyms defined as:

deathwatch and book louse: minute wingless psocopterous insects injurious to books and papers

Other synonyms of deathwatch include booklouse, Liposcelis divinatorius.

deathwatch (noun)	book louse (noun)
bores through wood making a ticking sound popularly thought to presage death	minute wingless psocopterous insects injurious to books and papers
minute wingless psocopterous insects injurious to books and papers