Lalaith
From the One Wiki to Rule Them All, the Lord of the Rings Encyclopedia.
Urwen, better-known by her nick-name Lalaith ("Laughter") was the second child of Húrin and Morwen and sister of Túrin.
Urwen was named Lalaith after the stream which ran by Húrin's house in Dor-lómin, because she was a happy child. She was compared to an Elven child by most people. Túrin loved his little sister, but she was killed by a plague which came to Hithlum from Angband when she was still an infant.
Túrin never got over her death and always looked for her likeness in women ever after, which is one possible reason for the tragedy which befell him when he took Níniel as a wife later.
