Значение идиомы says who

[says who] or [says you] {v. phr.}, {slang} I don’t believe oraccept that. – An expression of rebuff often used to make fun ofsomeone or oppose him.

“I am the strongest boy on the block.” “Saysyou.

“That brook is full of trout.” “Says who? I never sawanybody catch trout there.”

“You can’t take Mary to the party – she’s my girl.” “Says who?”