tarnish vs blot

tarnish and blot both are nouns.

Word	Noun	Adjective	Verb	Adverb
tarnish	Yes	No	Yes	No
blot	Yes	No	Yes	No

As verbs, blot is a hypernym of tarnish; that is, blot is a word with a broader meaning than tarnish:

tarnish: make dirty or spotty, as by exposure to air; also used metaphorically
blot: make a spot or mark onto

Other hypernyms of tarnish include blob, fleck, spot.

tarnish (noun)	blot (noun)
discoloration of metal surface caused by oxidation	an act that brings discredit to the person who does it
	a blemish made by dirt

tarnish (verb)	blot (verb)
make dirty or spotty, as by exposure to air; also used metaphorically	dry (ink) with blotting paper
	make a spot or mark onto