The Hebrew term lilith seems to have originally referred to a winged demon that preyed upon pregnant women and infants. During the Middle Ages, a legend—which had probably existed in some form for centuries—appears in Jewish sources to the effect that Lilith was Adam’s original wife, exiled from the Garden and replaced by Eve; eventually this story entered Christian mythology as well. Megan Sauter summarizes the recent scholarship about the story’s origins:
The creation of humans is described in the first two chapters of Genesis. The first account is fairly straightforward: “So God created humankind in his image, in the image of God He created them; male and female He created them” (Genesis 1:27). The second account describes how God formed man out of the dust of the ground and then creates woman [later given the name Eve] from the man. . . .
In the post-biblical period, some ancient Jewish scholars took the stance that Genesis 1:27 and Genesis 2:21–22 must describe two separate events, since it appears that woman is created differently in these accounts. . . . Accordingly, Genesis 1:27 describes the creation of Adam and an unnamed woman (Lilith); Genesis 2:7 gives more details of Adam’s creation; and Genesis 2:21–22 describes the creation of Eve from Adam.
Lilith’s creation is recounted in the Tales of Ben Sira, an apocryphal work from the 10th century CE. [The scholar] Dan Ben-Amos explains that although this is the first extant text that records the legend of Lilith, her story probably existed earlier.
Read more on Bible History Daily: http://www.biblicalarchaeology.org/daily/biblical-topics/hebrew-bible/lilith-in-the-bible-and-mythology/