Hi Peter, I'm an English womam married to a sardinian and living here is Sardinia. In the village that I live in there is a family called Marongiu.... I suppose the nearest explanation to the pronountion would be Maron (as in french for browm)and ju as in julie..... I hope that helps you ! As the name you gave as your ancester his name was probably Gian Costantino translated in modern terms... there is a village in the province of Nuoro called Sedilo where there is a sactuary called sant Costantino yor ancestor could have come form that area... just a bit of guess work. Do you know the name of his mother Agustino's wife ? The Italians even up to date keep their maiden name as their surname... I am still known as my maiden surname ...even if they pronounce it as Chaplin instead of Shepley....God know's the simularity! If you can find out what part of Sardinia Agostino came from then maybe I could help you.