livelihood vs bread and butter

livelihood and bread and butter both are nouns.

Word	Noun	Adjective	Verb	Adverb
livelihood	Yes	No	No	No
bread and butter	Yes	No	No	No

As nouns, livelihood and bread and butter are synonyms defined as:

Other synonyms of livelihood include keep, living, support, sustenance.

livelihood (noun)	bread and butter (noun)
the financial means whereby one lives	the financial means whereby one lives