Sea-Wing

The 'wing' in the name 'Sea-Wing' originally had a literal meaning, as names for the ship in earlier versions of Tuor's story were 'Swan-wing' and 'Eagle-wing'. In the final form, these references to birds were lost, but the 'wing' element remained as part of the ship's name. These details come from the early Lost Tales, which, it should be noted, is our only source for the description of the ship's purple sails (no colour is mentioned in later descriptions).

Assuming this story to be true, then Tuor and Idril might potentially have reached Aman more than a decade before their son Eärendil, in the voyage that saw him successfully plead for the aid of the Valar. This raises an obvious question: what prevented Tuor or Idril from achieving the same task? It seems that Eärendil's Half-elven blood was the critical factor, so that only a descendant of both Kindreds could achieve the destiny that had been assigned to him.