The shape is a diamond, pointed at the top, bottom, right and left. It represents something that is sparkling clean.
This shape is applied most often to oven buttons for the clean function. It was also used on a washing machine for the 'tub clean' function. Oh and I also applied it to a milk steamer appliance. Originally 'clean' was represented by a hand shape but as I labeled more and more appliances the diamond shape made more sense.
The design has rounded points because sharp points are, well, too sharp. Something to test in the future - straight edges. These edges are a bit curved which may be more pleasant but a crisp edge may better represent something that is clean.