The Hubbard-Stratonovich transformation is a nice way of eliminating squared terms in an exponential. It is heavily used in statistical mechanics. Essentially it boils down to the simple identity:
Wikipedia cites some references to works of Hubbard and Stratonovich justifying its name.
But I have also seen this transformation called "Feynman's trick". Although there are many things named "Feynman trick", for this in particular I could not find any Feynman paper actually exploiting this transformation. Can someone point to some references?