eau de cologne vs cologne water

eau de cologne and cologne water both are nouns.

Word	Noun	Adjective	Verb	Adverb
eau de cologne	Yes	No	No	No
cologne water	Yes	No	No	No

As nouns, eau de cologne and cologne water are synonyms defined as:

eau de cologne and cologne water: a perfumed liquid made of essential oils and alcohol

Other synonyms of eau de cologne include cologne.

eau de cologne (noun)	cologne water (noun)
a perfumed liquid made of essential oils and alcohol	a perfumed liquid made of essential oils and alcohol