That last one is the stumper. Nothing comes up in any of the dictionaries I checked, and a Google search turned up nothing useful as well.
体 = body 息 = breath 所 = place
If I were to take a spitball guess, it might have something to do with the position of Kaban-chan's rear and Serval-chan's face (i.e. orifices, places in the body where breath comes from).