cotter vs fastening

cotter and fastening both are nouns.

Word	Noun	Adjective	Verb	Adverb
cotter	Yes	No	No	No
fastening	Yes	No	No	No

As nouns, fastening is a hypernym of cotter; that is, fastening is a word with a broader meaning than cotter:

cotter: fastener consisting of a wedge or pin inserted through a slot to hold two other pieces together
fastening: restraint that attaches to something or holds something in place

Other hypernyms of cotter include fastener, fixing, holdfast.

cotter (noun)	fastening (noun)
fastener consisting of a wedge or pin inserted through a slot to hold two other pieces together	the act of fastening things together
a medieval English villein	restraint that attaches to something or holds something in place
a peasant farmer in the Scottish Highlands