knocker vs mudslinger

knocker and mudslinger both are nouns.

Word	Noun	Adjective	Verb	Adverb
knocker	Yes	No	No	No
mudslinger	Yes	No	No	No

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

knocker: one who disparages or belittles the worth of something
mudslinger: one who spreads real or alleged scandal about another (usually for political advantage)

Other hyponyms of knocker include backbiter, defamer, libeler, maligner, slanderer, traducer, vilifier, hatemonger, muckraker.

knocker (noun)	mudslinger (noun)
a device (usually metal and ornamental) attached by a hinge to a door	one who spreads real or alleged scandal about another (usually for political advantage)
either of two soft fleshy milk-secreting glandular organs on the chest of a woman
one who disparages or belittles the worth of something
a person who knocks (as seeking to gain admittance)
(Yiddish) a big shot who knows it and acts that way; a boastful immoderate person