It's a typical italian expression that is literally
translated as pig god referring god to a pig. It's mainly said to blame god for the things that happen either good or bad. The adjective "pig" can change into many other words such as merda(shit), cane(dog), bastardo (bastard), ladro (theif), stronzo(asshole) and so on. The expression can also involve the figure of the
virgin mary so the line can be Madonna puttana (referring the
virgin mary as a bitch). In certain regions of italy such as Tuscany and in the northern part of Italy, the expression is the equivalent of the filler words "fuck", "fucking"
Porco dio ho perso le chiavi - Porco dio
i lost my keys
Porco dio che bello rivederti - Porco dio i'm happy to see you
passami quel porco dio di
martello -
Hand me that fucking hammer.