iron heel vs the boot

iron heel and the boot both are nouns.

Word	Noun	Adjective	Verb	Adverb
iron heel	Yes	No	No	No
the boot	Yes	No	No	No

As nouns, iron heel and the boot are synonyms defined as:

iron heel and the boot: an instrument of torture that is used to heat or crush the foot and leg

Other synonyms of iron heel include boot, iron boot.

iron heel (noun)	the boot (noun)
an instrument of torture that is used to heat or crush the foot and leg	an instrument of torture that is used to heat or crush the foot and leg