beer barrel vs beer keg

beer barrel and beer keg both are nouns.

Word	Noun	Adjective	Verb	Adverb
beer barrel	Yes	No	No	No
beer keg	Yes	No	No	No

As nouns, beer barrel and beer keg are synonyms defined as:

beer barrel (noun)	beer keg (noun)
a barrel that holds beer	a barrel that holds beer