After giving up hope of finding the name of the interrobang in my mail - it was there, of course, but refused to be readily found - and even after a few Google searches didn't offer a solution, I settled for what I guess should have been the obvious route - the entry on Punctuation in Wikipedia.

That of course brought me not only to the name of the desired punctuation mark, but to the names of many others and links to them as well. And in keeping with the spirit of this particular Boidem column (and the Boidem in general) I suppose I can permit myself to follow the interrobang rabbit hole a bit further.