low-down vs scummy

low-down is a noun but scummy is not a noun.

Word	Noun	Adjective	Verb	Adverb
low-down	Yes	Yes	No	No
scummy	No	Yes	No	No

As adjectives, low-down and scummy are synonyms defined as:

Other synonyms of low-down include abject, low, miserable, scurvy.

low-down (noun)	scummy (noun)
slang terms for inside information

low-down (adjective)	scummy (adjective)
of the most contemptible kind	of the most contemptible kind
(of jazz) having the soulful feeling of early blues	covered with scum