fackins means used in exclamatory phrases to express surprise, insistence, etc. Lexicurio rates it Sui generis — a strength score of 89 out of 100.
noun
- Used in exclamatory phrases to express surprise, insistence, etc.“I proteſt— ― No, no, you ſhall not proteſt, couſſe. ― By my fakins, but I will, by your leave;[…]”