Conversation so far:
What role do priests play in Mandaeism?
There are three grades of priesthood in Mandaeism.
What are the three grades of priesthood?
the tarmidia "disciples" (Neo-Mandaic tarmidana), the ganzibria "treasurers" (from Old Persian ganza-bara "id.," Neo-Mandaic ganzebrana) and the risamma "leader of the people.
How does one become a priest?
CANNOTANSWER.
What are some differences between priests and laymen?
There is a strict division between Mandaean laity and the priests.
Why is there division?
the ignorant or semi-ignorant laity are called 'Mandaeans.
Is there any other interesting information regarding this topic?
The contemporary priesthood can trace its immediate origins to the first half of the 19th century.

Question: Where do the origins trace back to?
Self-contained rewrite: Where do the origins of Mandaeism trace back to?