come about vs effect

come about is not a noun while effect is a noun.

Word	Noun	Adjective	Verb	Adverb
come about	No	No	Yes	No
effect	Yes	No	Yes	No

come about (noun)	effect (noun)
	an outward appearance
	(of a law) having legal validity
	an impression (especially one that is artificial or contrived)
	the central meaning or theme of a speech or literary work
	a phenomenon that follows and is caused by some previous phenomenon
	a symptom caused by an illness or a drug

come about (verb)	effect (verb)
come to pass	produce
	act so as to bring into existence