baby vs do by

baby is a noun but do by is not a noun.

Word	Noun	Adjective	Verb	Adverb
baby	Yes	No	Yes	No
do by	No	No	Yes	No

As verbs, do by is a hypernym of baby; that is, do by is a word with a broader meaning than baby:

Other hypernyms of baby include handle, treat.

baby (noun)	do by (noun)
a project of personal concern to someone
a very young mammal
a very young child (birth to 1 year) who has not yet begun to walk or talk
the youngest member of a group (not necessarily young)
an immature childish person
an unborn child; a human fetus
a beloved person; used as terms of endearment

baby (verb)	do by (verb)
treat with excessive indulgence	interact in a certain way