Calid
Calid is a medieval Latin transcription of the Arabic name Khalid (or Khaled).
In alchemy, Kalid refers to a historical figure, Khalid ibn Yazid (died 704). He was an Umayyad prince, a brother of Muawiyah II who was briefly caliph. Prince Khalid lost the chance of inheriting the title, but took an interest in the study of alchemy, in Egypt. A book collector, he facilitated translations into Arabic of the existing literature. It is to this Khalid that later allusions to Calid rex (King Calid) refer.