For hundreds of years, people knew that castrated male chickens stayed tender and delicious instead of becoming not-so-tasty and not-so-friendly roosters.
The Asian cult of the Magna mater imported towards the end of the second Punic war in 205 BC included the self-castrated eunuch priests of their self-castrated god Attis. Ouch.
Among other things the law forbade the fattening of chickens because it was seen as a waste of grain so some enterprising young poulterer's instead castrated their roosters because that made them grow quite a bit larger.