ringer vs shammer

ringer and shammer both are nouns.

Word	Noun	Adjective	Verb	Adverb
ringer	Yes	No	No	No
shammer	Yes	No	No	No

As nouns, shammer is a hypernym of ringer; that is, shammer is a word with a broader meaning than ringer:

Other hypernyms of ringer include fake, faker, fraud, imposter, impostor, pretender, pseud, pseudo, role player, sham.

ringer (noun)	shammer (noun)
(horseshoes) the successful throw of a horseshoe or quoit so as to encircle a stake or peg	a person who makes deceitful pretenses
a contestant entered in a competition under false pretenses	someone shirking their duty by feigning illness or incapacity
a person who is almost identical to another
a person who rings church bells (as for summoning the congregation)