Literally: to drown the fish
Meaning: to beat around the bush, to muddy the waters, to cloud the issue.
Origins :End of 19th century, fishermen used this expression to describe a fishing technique, once hooked, you get the fish in and out the water to make him weaker.

There is also a literary reference to the author, Alphonse Daudet, whom contributed to make this expression popular, in his novel l’immortel. In this novel one of his character is the impostor and counterfeiter Vrain-Lucas, the perfect example for one capable to muddy the waters…and “de noyer le poisson”.
Synomyms: brouiller les pistes; tourner autour du pot