The NIghtingale Sings at night from the protection of the persimmon tree. (according to Shakespeare / Romeo and Juliet).
The symbolism reveals that green persimmons are acrid and bitter in their immature state, they represent ignorance. As the fruit matures, it becomes sweet and represents wisdom that comes after transformation.
So, Anons can associate the ignorant traitors going about evil activity for a time until they are brought in under cover of darkness, shown their crimes, and then with new knowledge and maturity, they then "sing".