the boot vs iron heel

the boot and iron heel both are nouns.

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

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

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

Other synonyms of the boot include boot, iron boot.

the boot (noun)	iron heel (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