In Dutch, some fables or fairy tales (or both) begin with the words "[lang geleden] toen de dieren nog spraken / konden spreken", i.e. "[a long time ago] back when the animals still spoke / could still speak". While it is not clear how common this type of introduction is in fable or fairy tales, it has been attested (though I know it mostly from texts that are decidedly not fairy tales or fables).
My question here is whether the origin of this phrase is known and, if yes, what that origin is.