Conversation so far:
What role do priests play in Mandaeism?
There is a strict division between Mandaean laity and the priests.
What are the three grades of priesthood in Mandaeism?
There are three grades of priesthood in Mandaeism: the tarmidia disciples, the ganzibria treasurers and the rišamma leader of the people.
How does one become a priest in Mandaeism?
Any ganzeḇrā who baptizes seven or more ganzeḇrānā may qualify for the office of rišamma, though the Mandaean community has yet to rally as a whole behind any single candidate.
What are some differences between priests and laymen in Mandaeism?
There is a strict division between Mandaean laity and the priests.
Why is there division between priests and laymen in Mandaeism?
The ignorant or semi-ignorant laity are called 'Mandaeans', Mandaiia—'gnostics.' When a man becomes a priest he leaves 'Mandaeanism' and enters tarmiduta, 'priesthood.'
Is there any other interesting information regarding Mandaeism aside from the division between priests and laymen?
The contemporary priesthood can trace its immediate origins.

Question: Where do the origins trace back to?
Self-contained rewrite: Where do the origins of contemporary priesthood inMandaeism trace back to?