I've seen it called "Bird in the Air". (It may have other names, too.) Here is a
video that calls it by that name and shows a neat way to make it that produces good accuracy for a lot of people. (The units are made a little large and trimmed down.)
If you leave out the line between units 1 and 4 of your image, it's know by a variety of names such as "Shaded Four Patch", Magic Square", "Hidden Square", "Mary's Triangles", "Square and Three Triangles" and "Jewel Box".