ruth vs fellow feeling

ruth and fellow feeling both are nouns.

Word	Noun	Adjective	Verb	Adverb
ruth	Yes	No	No	No
fellow feeling	Yes	No	No	No

As nouns, fellow feeling is a hypernym of ruth; that is, fellow feeling is a word with a broader meaning than ruth:

ruth: a feeling of sympathy and sorrow for the misfortunes of others
fellow feeling: sharing the feelings of others (especially feelings of sorrow or anguish)

Other hypernyms of ruth include sympathy.

ruth (noun)	fellow feeling (noun)
a feeling of sympathy and sorrow for the misfortunes of others	sharing the feelings of others (especially feelings of sorrow or anguish)