I'm not a computer graphics expert, but traditionally (since long before the latest 3D gaussian splatting) I've seen splatting used in computer graphics to describes a way of rendering 3D elements onto a 2D canvas with some "transparency", similar to 2D alpha compositing. I think the word derives from "splatter" - like what happens when you throw a tomato against a wall, except here you're throwing some 3D entity onto the camera plane. In the current context of 3D gaussian splatting, the entities that are splatted are 3D gaussians, and the parameters of those 3D gaussians are inferred with optimization at run time and/or predicted from a trained model.