the full version of the Oxford dictionary lists the earliest known uses of words, as prvided by readers of everything over the last century. They occasionally have TV programmes in which they ask for viewers' help in tracing words whose history they don't know.
It quotes an 1837 mention of jiggered (it also appears in Great Expectations) but says its origin is disputed. if you do come across an earlier mention, let them know and they'll include it.
But as I say, my own guess is that was spoken long before it was written, because people are more likely (in my view) to use euphemisms of this sort when speaking than when writing.