It is Italian: from Northern Italy, typical of Piedmont. In fact from TORINO (Turin). but originally this surname comes from a very little village of MONFERRATO area,SAN GIORGIO-MONFERRATO, near the city of ALESSANDRIA.
Most of the RABAGLINO immigrants in USA came from San Giorgio Monf.
And some families Rabaglino still live there (italian White Pages,
www.paginebianche.it/ tape AL for Alessandria).
No idea about the origin of this surname. Basically it could be a nickmname perhaps from "rapa" that is "turnip".
Variants (all in northern or Central Italy):
Rabaglia, Rabagli, Rabagliati (a popular singer of the 30ties), Rabaioli.
Important: in Monferrato you can drink very good wines!!