It would really, really help if you would include some context. Without context, it’s just a guess, so I’ll be brief: “Fiddle” refers to a violin when it’s used for folk music (as opposed to classical). “Yidl” (transliterated from the Hebrew alphabet) is a Yiddish (related to High German) diminutive meaning “Jew”, that is not usually known in English. Guessing, it appears to be a reference to the musical “Fiddler on the Roof”, and probably only makes sense if you are familiar with the musical.

Hello, Sonohri. "Yiddle" is the violinist in the song, and he is playing ragtime (music) on his fiddle (violin).

It's a name. "Yiddle" is the name of the fiddle (another word for violin) player.