peeper vs Peeping Tom

peeper and Peeping Tom both are nouns.

Word	Noun	Adjective	Verb	Adverb
peeper	Yes	No	No	No
Peeping Tom	Yes	No	No	No

As nouns, peeper and Peeping Tom are synonyms defined as:

peeper and Peeping Tom: a viewer who enjoys seeing the sex acts or sex organs of others

Other synonyms of peeper include voyeur.

peeper (noun)	Peeping Tom (noun)
an animal that makes short high-pitched sounds	a viewer who enjoys seeing the sex acts or sex organs of others
an informal term referring to the eye
a viewer who enjoys seeing the sex acts or sex organs of others