Where does “*bisacca” come from?

*bisacca (Vulgar Latin) comes from Late Latin bisaccium, from Latin bi-, from Proto-Italic *dwi- — two, bi-, di.

Ancestry of “*bisacca”, step by step

Step	Language	Word	Meaning
1	Late Latin	bisaccium	double saddlebag, twofold horse-holdall, wallet
2	Latin	bi-	having two parts; occurring twice
3	Proto-Italic	*dwi-	two, bi-, di