Wikipedia
Pseudo-Geber ("false Geber") is the name assigned by modern scholars to an anonymous European alchemist born in the 13th century (sometimes identified with Paul of Taranto), who wrote books on alchemy and metallurgy, in Latin, under the pen name of "Geber".
"Geber" is the shortened and Latinised form of the name Jābir ibn Hayyān, a 9th-century Islamic alchemist. In Europe for many centuries from the 14th century onward it was assumed that "Geber" was identical with Jabir ibn Hayyan and that the books of "Geber" had been translated from Arabic. Arabic alchemy was held in high esteem by 13th-century European alchemists. Pseudo-Geber adopted the name of his illustrious Arabic predecessor to attach more stature to his own work. The practice of adopting the name of an illustrious predecessor is called pseudepigraphy, and it was not uncommon in the medieval era. Similarly, a wide variety of medieval writings were distributed with the illustrious Aristotle as the stated author, which were not written by the original authentic Aristotle.
In the domain of alchemy and metallurgy in late medieval Europe, Pseudo-Geber's output was highly influential, arguably more influential than any other author.