From the french
expression : "anguille sous roche" that tell : "There is a
snake in the grass."
But the second
metaphore that tell there is Rocco like "Rocco Sifreddi" referred to the italian pornstar.
So the meaning explain that there is something hidden about a sexual thing.
Tom : I met a really cool girl last night,, he was pretty handsome, we chat
all night long !
Chloé : Shhhhhhh ,
don't tell me that ! I know there is a anguille sous rocco heheheh
Tom : Please no comment ahahaah you
embarassed me !