From Greek mythology. Philomela and Procne were sisters. Procne
married King Tereus. Tereus raped Philomela and cut out her tongue to
silence her. Philomela weaved her story into some cloth to tell her
sister what happened. Procne fed their son to Tereus as punishment.
The sisters fled, with Tereus in pursuit. The gods intervened,
changing Philomela into a nightingale, Procne into a swallow, and
Tereus into a hawk (some versions of the myth vary this.)