croak vs buy it

croak is a noun but buy it is not a noun.

Word	Noun	Adjective	Verb	Adverb
croak	Yes	No	Yes	No
buy it	No	No	Yes	No

As verbs, buy it is a hyponym of croak; that is, buy it is a word with a more specific, narrower meaning than croak:

croak: pass from physical life and lose all bodily attributes and functions necessary to sustain life
buy it: be killed or die

Other hyponyms of croak include abort, asphyxiate, stifle, suffocate, pip out, drown, predecease, famish, starve, fall, succumb, yield.

croak (noun)	buy it (noun)
a harsh hoarse utterance (as of a frog)

croak (verb)	buy it (verb)
pass from physical life and lose all bodily attributes and functions necessary to sustain life	be killed or die
make complaining remarks or noises under one's breath
utter a hoarse sound, like a raven