Les carottes sont cuites, literally “The carrots are cooked”, conveys the idea that there is little hope left, that nothing can be done to change it. The best English equivalent would be “The goose is cooked”.
The expression dates back to the 18th century. The poorest part of the population would often eat meat and cooked carrots as these were cheap. In times of scarcity of food, people were sometimes confined to eat only cooked carrots and that was a sign of bad times…
French with Valerie 