Her mantle glinted in the moon,
As on a hill-top high and far
She danced, and at her feet was strewn
A mist of silver quivering.
When winter passed, she came again,
And her song released the sudden spring,
Like rising lark, and falling rain,
And melting water bubbling.
He saw the elven-flowers spring
About her feet, and healed again
He longed by her to dance and sing
Upon the grass untroubling.
Again she fled, but swift he came.
Tinúviel! Tinúviel!
He called her by her elvish name;
And there she halted listening.
One moment stood she, and a spell
His voice laid on her: Beren came,
And doom fell on Tinúviel
That in his arms lay glistening.

As Beren looked into her eyes
Within the shadows of her hair,
The trembling starlight of the skies
He saw there mirrored shimmering.
Tinúviel the elven-fair,
Immortal maiden elven-wise,
About him cast her shadowy hair
And arms like silver glimmering.
Long was the way that fate them bore,
O'er stony mountains cold and grey,
Through halls of iron and darkling door,
After several encounters in the woods, Lúthien frightened and not fully aware of who her admirer was (and many thwarted by her companion and general cock-block Daeron), with Beren calling her Tinúviel (“Daughter of Twilight”) with great longing, she at last gazed upon Beren, and fell in love with him immediately. 
 This, however, caused her doom, as she had fallen in love with a mortal man, and one hounded by Morgoth and his servants no less. 
 This is also the first time a mortal and immortal had fallen in love, and such a coupling required ultimately that Lúthien sacrifice her immortality. 
 This of course is strongly reminiscent of the love affair between their descendents, Aragorn and Arwen. 
 Tolkien based the hostility of Thingol to Beren on his own encounters courting Edith – her Protestant family strongly disapproved of his Catholic faith, and his guardian forbade him contact her until he turned 21. So, on J.R.R.’s twenty-first birthday, he sent her a telegram proposing marriage. Although Edith was already engaged, she sent back the ring and accepted Tolkien’s proposal.