locker vs holdfast

locker and holdfast both are nouns.

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

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

Other hypernyms of locker include fastener, fastening, fixing.

locker (noun)	holdfast (noun)
a storage compartment for clothes and valuables; usually it has a lock	restraint that attaches to something or holds something in place
a trunk for storing personal possessions; usually kept at the foot of a bed (as in a barracks)
a fastener that locks or closes