and so forth vs and so on

and so forth and and so on both are adverbs.

Word	Noun	Adjective	Verb	Adverb
and so forth	No	No	No	Yes
and so on	No	No	No	Yes

As adverbs, and so forth and and so on are synonyms defined as:

Other synonyms of and so forth include etc., etcetera.

and so forth (adverb)	and so on (adverb)
continuing in the same way	continuing in the same way