honest-to-god vs honest-to-goodness

honest-to-god and honest-to-goodness both are adjectives.

Word	Noun	Adjective	Verb	Adverb
honest-to-god	No	Yes	No	No
honest-to-goodness	No	Yes	No	No

As adjectives, honest-to-god and honest-to-goodness are synonyms defined as:

honest-to-god and honest-to-goodness: (used informally especially for emphasis) real or genuine

Other synonyms of honest-to-god include sure-enough.

honest-to-god (adjective)	honest-to-goodness (adjective)
(used informally especially for emphasis) real or genuine	(used informally especially for emphasis) real or genuine