Green’s Dictionary of Slang

1. to come to grief, to fail.

1862

H. Kingsley Ravenshoe 94: Welter has muckered [...] but worse than that, they say that Charles Marston’s classical first is fishy .

2. to ruin.

1890

Bird o’ Freedom 22 Jan. 4: Don’t get adding any bacon, or thick gravy, or you’ll mucker the dish.