Green’s Dictionary of Slang

dog’s meat n.

also dog meat
[otherwise good enough only for the dogs]

1. [late 16C–19C; 2000s] anything considered worthless, e.g. a badly written book, a poorly executed painting etc; also a despicable person; also as adj.

2. [1960s+] (S.Afr.) domestic workers, lit. cheap cuts of meat which are cooked for the servants’ meals.

3. in fig. use, a dead person, a person in serious trouble.