butterbean vs sieva bean

butterbean and sieva bean both are nouns.

Word	Noun	Adjective	Verb	Adverb
butterbean	Yes	No	No	No
sieva bean	Yes	No	No	No

As nouns, butterbean and sieva bean are synonyms defined as:

Other synonyms of butterbean include butter bean, civet bean.

butterbean (noun)	sieva bean (noun)
small flat green bean similar to lima beans	small flat green bean similar to lima beans
	bush bean plant cultivated especially in southern United States having small flat edible seeds