The basis of the story of Alraune dates to the Middles Ages in Germany. The humanoid-shaped mandrake root, or Mandragora officinarum, was widely believed to be produced by the semen of hanged men under the gallows.
Alchemists claimed that hanged men ejaculated after their necks were broken and that the earth absorbed their final "strengths". In some versions, it is blood instead of semen.
The root itself was used in love philtres and potions while its fruit was supposed to facilitate pregnancy. Witches who found the Death-grown Mandrake root were said to use it in a brew that would impregnate them with offspring that had no feelings of real love and no soul. This myth was one of the many reasons people, of Germany specifically, disapproved of women who bore children out of wedlock and gave them reason to shun, abuse, & burn them when they believed their children to be monsters.
The most prevalent example of the myth in modern culture is Hanns Heinz Ewers's 1911 fiction novel 'Alraune', which follows themes of genetics vs environment through the tale of a girl, Alraune, who was artificially inseminated into a prostitute using a hanged man's semen and was raised by the scientist who thought of the procedure. The book gained a movie adaptation in 1918 and in 1928. In modern pop culture, the Alraune is commonly portrayed as a mandrake plant-human hybrid being, usually seen as female.