Some people asked me some questions about different names in the Tolkien world, I'll briefly try to answer them in this post.
First of all, who is Elendur?
In the stories of Tolkien two people go by the name of Elendur. The first is Elendur, son of Isildur (the guy that took the ring in the opening scene of the movie, but was murdered in that very scene...). He fought with his father and brothers and uncle and grandfather in the battle of the Last Alliance. After Isildur took the ring, he counselled his father to throw it away in the fires of Mount Doom. His father didn't listen. It is noted that Elendur had a striking resemblance with his grandfather Elendil. Elendur was killed along with his father and his brothers Aratan and Ciryon in the disaster of the gladden fields.
The second Elendur was a king of Arnor who ascended the throne in 652TA. Not much of him is known except his birthyear (552 TA) and that he died in 777 TA. He was the father of Eärendur, the last king of Arnor before the kingdom was split in three parts; Arthedain, Cardolan and Rhudaur.
Next question, who was Ereinion? Ereinion is actually more a title, than a name. It was the Kingsname of Gil-Galad and means "descendant of kings", this was of course applicable to Gil-Galad because he was of the house of finarfin. He became high king of the Noldor after the death of Turgon.
