etiquette vs protocol

etiquette and protocol both are nouns.

Word	Noun	Adjective	Verb	Adverb
etiquette	Yes	No	No	No
protocol	Yes	No	No	No

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

etiquette: rules governing socially acceptable behavior
protocol: forms of ceremony and etiquette observed by diplomats and heads of state

Other hyponyms of etiquette include punctilio, netiquette.

etiquette (noun)	protocol (noun)
rules governing socially acceptable behavior	code of correct conduct
	forms of ceremony and etiquette observed by diplomats and heads of state
	(computer science) rules determining the format and transmission of data