It’s the shape used to package small portions of things like sour cream (you get one with a baked potato at Wendy’s); also, some public school frozen orange juice popsicles from my youth. It’s a nifty package: usually one end is perforated; just tear off the end strip and squeeze from the opposite end.
The shape is a [bi-?]symmetrical form that’s like two wedges morphing into each other at a 90-degree angle. It’s kinda triangular, and pyramidal, without being either. Does it have a name?
The ice lolly that I immediately thought of that comes in these tubes is the Calippo.
Googling around that, it seems the industry just tends to call them “calippo-type” or “calippo-style” tubes. I don’t think the shape itself has a name, as such. I propose that it should be called a callipsoid. 
OK, I now see that the Wendy’s carton is not really the same thing. But that does look a lot like the pyramid tea bags that you can get nowadays.
Is this what you mean? As far as the shape goes, I mean.
It sounds like a stretched Tetrahedron. a Regular Tetrahedron is the shape you generate by taking equilateral triangles and putting them together so that three faces meet at each corner. Each edge will be opposite an edge that sits at 90 degrees to the first edge. It’s the shape you can easily generate by pinching off a tuve, filling a portion of the tube with material, then pinching the other end off along a line that’s at right angles to the first pinch-off. A nifty way to generate a volume that’s not easily squeezed flat.
What Cal said.
I found this site here.
Must be cool if it is in the MoMA.
Adam yax just beat me to it, but this is indeed the original “tetrahedral paper carton” that gave its name to TetraPak. Link - see bottom of page.
The Calippo tubes are just a very elongated form of this, really, but with the short end formed into a cylindrical opening that is then capped with a foil lid.
Gad, I love these boards. Just re-upped last week and I’ve already got my money’s worth.
adam yax’s linked pic is exactly what I had in mind. Sorry I’ve been absent from this thread, guys, but I’ve been looking through Google Images for a pic (and came up empty).
“Stretched tetrahedron,” eh? Now, that’s the sort of geeky trivia I love to drop into casual conversation… Thanks, all! 
If you want to be a little more precise, you could call it an isoceles tetrahedron, since all of the faces are isocelese triangles.
Or more precisely still, isosceles tetrahedrons. (I don’t know shapes, but I do know spelling!) 
