What's the correct name for a geometric solid that's a beanbag?

Question

My daughter is in the first grade, and I'm having a good deal of fun trying to determine the shapes of irregular geometric solids. I'm stuck on the good, old beanbag.

Here are the parameters.

1. Theoretically, it's a rectangular prism, a cuboid of sorts.
2. But when I sewed it (it was originally two 2-dimensional pieces of cloth, and turned it inside out it became not square but octagonal (b/c we didn't push out the edges all the way).
3. Then we filled it (with beans), and it makes a hexagonal pillow shape as seen in the pictures.
4. I'm working on trying to determine the correct nomenclature for, using things things like lists of polyhedra, but the "roundness" of the bag, its "convex elongated"? quality makes me wonder what, really, is is. http://en.wikipedia.org/wiki/List_of_uniform_polyhedra
5. Essentially, it's like giving a name to a kind of pillow. I tried to post photos here but was unable to...

Any thoughts are most helpful! Thanks, Julie

Answer 1

I found this paper which calls it a "square pillow" (section 6.2). Because of the rounded corners one might call it a "truncated square pillow" by analogy to polyhedra nomenclature. The paper seems to be about polyhedra inflated with (mathematical) air rather than stuffed with beans, but the images on page 11 look very similar, aside from the corners. Note that the "square pillow" is not a polyhedron. A polyhedron that I think resembles this shape is the square orthobicupola.