You would not say "In the year eighteen and something", since that would not conform to the standard way of reading years. We don't put an "and" except after "hundred". In standard English we normally would say either:
In the year eighteen something
In the year eighteen hundred and something.
You could use "something", "thus and such", "and such", "some", or any similar phrase. The choice really depends on the register of the work and the interpretation you wish to give it (which might be out of scope for this board). Just consider that "mumble mumble" is extremely informal and perhaps comic, and "thus and such" is more formal and perhaps stilted.