Is there a term for the use of an unnecessary or redundant adjective?

Solution 1:

Yes, the correct term is pleonasm. These adjectives are pleonastic.

Pleonasm - is the use of more words or parts of words than is necessary for clear expression

It is often used rhetorically for emphasis. It is also common in pro-drop languages for emphasis.

There is one particularly notable example of this rhetorical construction. In the Greek Bible there is a big deal made about the various "I am" statements made by Jesus, "I am the way the truth and the light" etc. The Greek specifically says "ἐγώ εἰμί" which has a pleonastic pronound "ἐγώ" which is to say that it means the same even if you drop the pronoun, Greek being a pro-drop language. This marks the expression out as rhetorically significant and supposedly is an allusion to Exodus 3:14, which, ironically, does not have a pleonastic pronoun, even though Hebrew is also pro-drop.