buckle vs holdfast

buckle and holdfast both are nouns.

Word	Noun	Adjective	Verb	Adverb
buckle	Yes	No	Yes	No
holdfast	Yes	No	No	No

As nouns, holdfast is a hypernym of buckle; that is, holdfast is a word with a broader meaning than buckle:

buckle: fastener that fastens together two ends of a belt or strap; often has loose prong
holdfast: restraint that attaches to something or holds something in place

Other hypernyms of buckle include fastener, fastening, fixing.

buckle (noun)	holdfast (noun)
fastener that fastens together two ends of a belt or strap; often has loose prong	restraint that attaches to something or holds something in place
a shape distorted by twisting or folding

buckle (verb)	holdfast (verb)
bend out of shape, as under pressure or from heat
fasten with a buckle or buckles
fold or collapse