Lady of the Star-brow
From Tolkien Gateway
A title given to Erendis in Númenor after her betrothal to Aldarion, 'Lady of the Star-brow' is a direct translation of the Elvish Tar-Elestirnë. The name comes from the fact that, at that time, Erendis took a diamond from Middle-earth (an earlier gift from Aldarion) and bound it to her brow with a silver fillet.
Erendis' 'Star-brow' served to found a tradition in Númenor, and we're told that after her time the Kings and Queens would wear a white jewel as a star on their brows, in place of a crown.