Witch-king of Angmar was born in middle of the second century, but nobody knew where he was born, his lineage and the exact time. In 1697, Sauron took Eregion down and got the nine rings.
Sauron gave men the nine rings and they became the greatest King, magician, and worrier at that time; however, no matter what their original intension to accept ring is good or bad, and power of the ring slowly corrupted them. At the end, they became immoral Nazgûls who drifts between the ground and death and were bound to Sauron as slave.
In 2251, it’s the first time that Nazgûl showed up in the middle continent. At the third century, Sauron started over in the Dol Gukdur and Nazgûl came around.
Nazgûl is another name for the Ringwraiths. Also called The Nine, and Black Riders.