restrain vs fetter

restrain is not a noun while fetter is a noun.

Word	Noun	Adjective	Verb	Adverb
restrain	No	No	Yes	No
fetter	Yes	No	Yes	No

As verbs, fetter is a hyponym of restrain; that is, fetter is a word with a more specific, narrower meaning than restrain:

restrain: to close within bounds, or otherwise limit or deprive of free movement
fetter: restrain with fetters

Other hyponyms of restrain include bind, tie down, tie up, truss, shackle, enchain, pinion, shackle, impound, pound, pound, pound up, fold, pen up, ground.

restrain (noun)	fetter (noun)
	a shackle for the ankles or feet

restrain (verb)	fetter (verb)
prevent the action or expression of	restrain with fetters
to close within bounds, or otherwise limit or deprive of free movement
restrict (someone or something) so as to make free movement difficult
prevent (someone or something) from doing something