Fun fact: peacocks are absolutely kosher, and the fact that they are kosher is directly related to the turkey thing.
Ever notice how most words for turkey seem to imply that they are a bird from India or the East, when they most certainly are not? Obviously there's the English word "Turkey" (it's not a coincidence that both the bird and the country are called that!) but there's also:
French: "dinde" -> "from India"
Turkish: "hindi" -> "from India"
Russian: "индейка" -> "from India"
Polish: "Indyk" -> from India"
Georgian: "ინდაური" -> "from India”
Greek: "διάνος" -> "from India"
Hebrew: "תרנגול הודו" -> "Indian rooster"
Norwegian: "kalkun" -> "from Calcutta"
Swedish: "kalkon" -> "from Calcutta"
Danish: "kalkun" -> "from Calcutta"
Icelandic: "kalkúnn" -> "from Calcutta"
Estonian: "kalkun" -> "from Calcutta"
Lithuanian: "kalakutas" -> "from Calcutta"
Dutch: "Kalkoen" -> "from Calcutta"
Then we have a pattern breaker which is actually a hint as to why these birds are so associated with India: In Arabic it's either "ديك حبش" -> "Ethiopian rooster" or "ديك رومي" -> "Roman rooster".
And then perhaps most damningly, the Spanish word for Turkey is literally "pavo" (peacock), and the word got so devalued post-Columbian exchange that they needed a whole new word for real peacocks, "pavo real" (royal peacock).
Peacocks were a big ticket banquet item that people had heard about kings and emperors feasting on. They were the height of decadence. You couldn't afford them, but you'd heard that people who could had them imported from far off lands like India and Ethiopia.
Turkeys are a New World bird, and they're as big as peacocks and look closer than literally anything else on the market. Some of them are even sort of colorful like one, kind of! And they grow like a weed, so they're shockingly affordable to raise. So, if you're an enterprising poultry merchant, what do you tell people that this enormous bird you have is? Well, it's a peacock, of course! Just like the Romans ate at their grand banquets, just like they're eating in far-off India. You too can now dine like a king for the low, low price of [ridiculously over-priced turkey].
It was poultry fraud, basically. Probably mixed with some genuine confusion, because even the travelers who went to the New World at the time certainly were confused about what turkeys were and what they were related to... but since the going theory at the time was that they were some relative of the guinea hen (they aren't), and the guinea hen is from African, not India, I really doubt that it was all just honest confusion.
So, how does this connect to turkey being kosher?
Well, you see, for a bird to be kosher, it needs to:
Not be on the biblical list of treif birds
Not share qualities with those birds such as being birds of prey
There has to be a living tradition of Jews eating it
Now, turkey passes criteria 1 and 2 with flying colors, but 3 seems literally impossible without some Mormon historical revisionism...
...Except that peacocks and guinea hens were both already kosher birds. And by the time everyone figured out that these weird, cheap peacocks that had hit the markets were not actually any species of peacock at all, there was a living tradition of several generations of Jews eating them, because at the time they'd thought that they were eating a weird New World peacock, not a completely unrelated bird.
So we have fraud to thank for kosher turkey, basically, thank you for coming to my TED talk.
