The date of Elendur's birth appears only in The History of Middle-earth volume XII, The Peoples of Middle-earth. It cannot therefore be considered completely reliable.

Elen- can mean either 'star' or 'Elf' depending on context, but in Elendur's case it is almost certainly 'star'. The reference remains unexplained, but it perhaps refers specifically to the Star of Eärendil rather than to stars in general, especially as Eärendil was Elendur's distant ancestor. However, Elendur shared his name with, and was possibly named for, Elendur the eldest son of Isildur. That earlier Elendur's name seems to mean 'devoted to the stars' in general, following the celestial tradition of his father Isildur and uncle Anárion, whose names devoted them to the Moon and Sun respectively.

The ending -ndur usually means 'servant', but in this context can be taken as something like 'devotee' or 'follower' (in the same sense that Elendur's father Valandur was a 'servant of the Valar').