décrocher le cocotier
“Décrocher le cocotier” means literally “to unhook the coconut tree” or “to take down the coconut tree.” In English, it means “to achieve one’s goals, to win a prize, or to triumph.” An equivalent English expression would be “to hit the jackpot.”
The saying dates from the 19th century. It refers to greasy pole competitions in the local village, where a tall pole would be greased with tallow. At the top of the pole would be some kind of prize, such as food or a silver cup (known as a “timbale”). Any man who succeeded in reaching the top would be entitled to claim the food or the silver cup.
Another related French idiom is “décrocher la timbale,” which means “to unhook the (silver) cup.”