constrain vs fetter

constrain is not a noun while fetter is a noun.

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

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

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

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

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

constrain (verb)	fetter (verb)
severely restrict in scope or extent	restrain with fetters
to close within bounds, or otherwise limit or deprive of free movement
compel to behave in a certain way