know as vs nickname

know as is not a noun while nickname is a noun.

Word	Noun	Adjective	Verb	Adverb
know as	No	No	Yes	No
nickname	Yes	No	Yes	No

As verbs, nickname is a hyponym of know as; that is, nickname is a word with a more specific, narrower meaning than know as:

Other hyponyms of know as include baptise, baptize, christen, refer, style, title, dub, rename, entitle, title, term, tag.

know as (noun)	nickname (noun)
	a familiar name for a person (often a shortened version of a person's given name)
	a descriptive name for a place or thing

know as (verb)	nickname (verb)
look on as or consider	give a nickname to
assign a specified (usually proper) name to