Abracadabra historically was believed to have healing powers when inscribed on an amulet.
The first known mention of the word was in the third century AD in a book called Liber Medicinalis (sometimes known as De Medicina Praecepta Saluberrima) by Quintus Serenus Sammonicus,physician to the Roman emperorCaracalla, who in chapter 51 prescribed that malaria sufferers wear an amulet containing the word written in the form of a triangle.
The power of the amulet, he explained, makes lethal diseases go away. Other Roman emperors, including Geta and Alexander Severus, were followers of the medical teachings of Serenus Sammonicus and may have used the incantation as well.
It was used as a magical formula by the Gnostics of the sect of Basilides in invoking the aid of beneficent spirits against disease and misfortune. It is found on Abraxas stones which were worn as amulets. Subsequently, its use spread beyond the Gnostics.