
These diagrams come by different names: "banana", "water melon", "basket ball". An early reference is M. Creutz, Rev. Mod. Phys. 50, 561–571 (1978). A more recent reference is S. Groote, J.G. Körner, A.A. Pivovarov (1998).
There is a long tradition of giving fancyful names to Feynman diagrams. This is the sunset diagram:




