No suitable person is known to be original for this. Probably intended as a substitute for hell or, more fully, for "damned hell".
One possibility for the origin of this expression is from the Swedish word for "community" which is "samhället". Some Swedish immigrant to the United States might have said, "Nu ver in de samhället has Johnny gone to?!", and it became anglicized, repeated, and immortalized.
- (slang) Intensifier.
- What the Sam Hill do you think you're doing?
- Who the Sam Hill does he think he is?
- Where in Sam Hill is that dog off to?
- 1960, Harper Lee, To Kill a Mockingbird, ch. 3,
- Walter poured syrup on his vegetables and meat with a generous hand. He probably would have poured it into his milk glass had I not asked what the sam hill he was doing.