Diddly is a slang term that refers to something that is of little or no importance or value. There are several synonyms that can be used instead of diddly, including trifle, insignificance, and triviality. Another synonym for diddly is a mere, which implies something that is small, insignificant, or barely noticeable. A couple of other synonyms for diddly include pittance and jot, which both refer to small amounts or quantities. Finally, the word nil can also be used as a synonym for diddly, as it refers to an absence or lack of something and can be used to convey the sense of insignificance or unimportance.