I believe it's called 'line breeding' in chickens...don't compare it to human incest.
:gig funny, but not....
Do you really think it's still common there or just a derogatory colloquial insult carried over from days way gone by?
Or call them gumbo, nuggets, etc.
It's a mind set and if names (or not) help go for it.
I found it truly gratifying to eat extra cockerels instead of begging other people to take them....tho yes it was hard to kill them, even harder for the older hens.