It used to be that one of the treatments for insanity was to lower the person into a pit of snakes....
The belief being that if it would scare a sane person crazy, it would scare a crazy person sane. What it did do was show up the fakes. The poor, truly insane person was either oblivious, or scared deeper into madness.
That is where the term snake pit came from.
I was trying to discover who initially used the "snake pit" practice, and it looks like it dates to the middle ages, but not thereafter. I guess I was thinking in terms of snake oil as being the "cure all for what ails ya", which would cover all diagnoses.