TNN's are indeed Transylvanian Naked Necks. The National breed of Romania and, despite what Kimbo thinks, are to my mind one of the prettiest chickens you can get. Whilst the bare neck detracts somewhat, their graceful and delicate movements more than make up for it. They remind me of the 4 'Beatles' vultures in Jungle Book. Quite small birds really but incredibly strong, even picking up the hens can be a real struggle. Their lack of feathers makes dressing them for the table quite easy. They are surprisingly hardy but the hens, as previously said, can go broody almost on a weekly basis and stop laying which means eggs are infrequent, so 120 a year is the best you will get. They are one of the components of the French National broiler breed, the Cou-Nu, which is a vicious thing and about twice the size. The lack of feathering all over the body is the result of a naturally occurring feather depleting hormone which collects in certain areas under the skin. They can be very territorial and very noisy, constantly squabbling over the presence of another hen in 'their' nestbox, who they will try to remove even though they don't wish to lay themselves.
Ours are all black, although the natural colour of the cocks is black with dark brown wings and hackles. The French version is light brown, black or white, the latter of which is the only permitted show colour here. In the UK any neck feathering on the TNN is a major defect and can be the result of cross breeding. In France the Cou-Nu must have a ruff of feathers about 2/3rds the way down the neck and any lack of feathering there is a major defect.