Etched Finish Removed from Porcelain Floor
The pure porcelain as well as ceramic tiles are unetchable, but the coat or finish on it can be easy stripped off. In such case it may look like genuine etch, but actually the part of the finish was unevenly removed.
Also on old tiles, especially on a kitchen floor over time can be formed a thin layer of grease and dirt, and if you spilled a strong cleaner or chemical, that layer of grease will be cleaned out, and there will be different colors in shape of spill. So it may look like etching as well.