namby-pamby vs wishy-washy

namby-pamby is a noun but wishy-washy is not a noun.

Word	Noun	Adjective	Verb	Adverb
namby-pamby	Yes	Yes	No	No
wishy-washy	No	Yes	No	No

As adjectives, namby-pamby and wishy-washy are synonyms defined as:

Other synonyms of namby-pamby include gutless, spineless.

namby-pamby (noun)	wishy-washy (noun)
an insipid weakling who is foolishly sentimental

namby-pamby (adjective)	wishy-washy (adjective)
lacking courage or vitality	lacking courage or vitality