The frog tells the nightingale that her song must be her own while he himself does not let her use her skill and talent in this field. He has restricted her entire freedom. Here lies the irony of the statement. In the beginning when the nightingale confesses that her song was original, he immediately demeans her and tells her that it was nothing to boast about. Then after killing the nightingale, the frog puts the blame on the nightingale saying that she should have been original.
