The Quenya name of S. Elros (PM/349), a compound of elen “star” and rossë “dew”. The final -n of elen was assimilated to the r, which also happened in the names Elerondo and Elerrína.
Quenya
Elerossë
star foam
elerossë
masculine name. Star Foam
Elerossë masc. name, "star foam", starlit foam, Sindarin Elros(PM:348)