XDA reports that the mention of the Italian dessert was found in an AOSP commit, in a line that simply reads “Rename T to Tiramisu”. As mentioned earlier, this will likely remain a name that’s used only internally.

Google used to name its Android mobile OS versions after desserts, even publicly. This stopped with Android 10, which was simply known to the public as Android 10. Though internally, the company still referred to it as Quince Tart. It’s much the same for Android 11 and 12, as even if the public only knows them by their number, they were referred to internally as Red Velvet Cake and Snow Cone, respectively. And that’s about all we know about Android 13 for now. Which is only natural, since Android 12 is not even out yet for the public, with its third beta version being just released recently. And things will likely remain this way for a considerable amount of time. (Source: XDA)

Android 13 Is Known Internally As Tiramisu - 3