Laila, Layla, Leila, Lejla, Laela, Laelah, or Leyla (Arabic: ليلى, Hebrew: לילה) is a feminine given name originating in the Arabic language but now used internationally. The name is derived from the tri-consonantal root: ל-י-ל (Lamedh-Yodh-Lamedh) L-Y-L and means "night"; over time it has been taken to mean "Born at Night," "Dark-haired Beauty" or "Dark Beauty." 
The name has long been used in Arab and Persian folklore, poetry, and literature. For example, the 7th-century Arab poet Qays addressed romantic poems to a woman called Layla. The story of Qays and Layla or Layla and Majnun became a popular romance in the medieval Arab World and Persia, and use of the name spread accordingly; it gained popularity further afield in the Muslim World, among the Turkic peoples and in the Balkans and India.
It has also acquired a following in the English-speaking world, especially after the 1970 hit song "Layla" by Derek and the Dominos, the title of which may have been inspired by the medieval romance.
In the Nordic countries, Laila or Lajla (pronounced lie-lah) is derived from the Sami name Láilá, the Sami variant of Helga which means holy.
The name Lailah is the same as the Hebrew word for "night", laylah (לילה). The identification of the word "night" as the name of an angel originates with the interpretation of "Rabbi Yochanan" (possibly Yochanan ben Zakkai, c. 30–90 AD) who read "At night [Abraham] and his servants deployed against them and defeated them” (Genesis 14.14, JPS) as "by [an angel called] night" (Sanhedrin 96a).