Here's the breakdown:
* Disapprove is the base verb meaning "to have a negative opinion of something."
* Disapproving is the present participle form, indicating the action of disapproving.
* Disapprovingly is an adverb, meaning "in a way that shows disapproval."
So, the root word is "approve" with the prefix "dis-" added to indicate negation, and the suffix "-ingly" to turn it into an adverb.