Eladar (S. 'Star-father') was one of the epithets of Tuor. It referred to his son, Eärendil, who became the star Gil-Estel.
The name contains the elements el and adar.
 See also
J.R.R. Tolkien, Christopher Tolkien (ed.), The War of the Jewels, "Part Two. The Later Quenta Silmarillion: Of the Coming of Men into the West (Chapter 14)", (ii) The House of Hador, p. 235