Is "I'm'nt" a thing?

I actually once saw a double contraction like that, with two apostrophes, in a piece of 19th century writing. I might have been one of Jane Austen's letters. I don't remember what word it was. I think they used lots of abbreviations and contractions because paper was scarce and expensive.

I’m’nt be telling yess’in ‘er no.

it is now