Any New York blood in your family? (Not that it necessarily matters as the term could have been used in England). Complete guesstimate but maybe someone in your family used to call mince “chop meat” (New York term for it) choppy and the sayings born out of that? Chopped meat is mangled and pretty nasty looking when you buy it and it would probably have been normal to go to a butchers to buy meat as you wanted it and would have come in bags. Seems like a logical progression to “she looks like a bag of choppy” for saying someone looks awful?

As for chin cough; much more definitely it’s another term for whooping cough, used in the north of England. Seems to have origins as either a scots word (chinkough?) or from “chink cough” presumably comparing Chinese speech patterns with the cough (it was added to the dictionary in 1913 but could have been around in everyday speech since the Opium Wars in the mid 1800s) depending where you look.