tam-o'-shanter vs tam

tam-o'-shanter and tam both are nouns.

Word	Noun	Adjective	Verb	Adverb
tam-o'-shanter	Yes	No	No	No
tam	Yes	No	No	No

As nouns, tam-o'-shanter and tam are synonyms defined as:

Other synonyms of tam-o'-shanter include tammy.

tam-o'-shanter (noun)	tam (noun)
a woolen cap of Scottish origin	a woolen cap of Scottish origin