Jacob's ladder vs jack ladder

Jacob's ladder and jack ladder both are nouns.

Word	Noun	Adjective	Verb	Adverb
Jacob's ladder	Yes	No	No	No
jack ladder	Yes	No	No	No

As nouns, Jacob's ladder and jack ladder are synonyms defined as:

Jacob's ladder and jack ladder: (nautical) a hanging ladder of ropes or chains supporting wooden or metal rungs or steps

Other synonyms of Jacob's ladder include pilot ladder.

Jacob's ladder (noun)	jack ladder (noun)
(nautical) a hanging ladder of ropes or chains supporting wooden or metal rungs or steps	(nautical) a hanging ladder of ropes or chains supporting wooden or metal rungs or steps
pinnate-leaved European perennial having bright blue or white flowers