Dividing out which occupations are professions and which are not is a tough job these days. As Andrew Abbott demonstrated in the excellent The System of Professions, occupations compete with one another to claim professional status. New jobs invent official credentials in order to professionalize.
I try to stick to the classic professions: clergy, military (officers), doctors, lawyers. The teaching profession derives from the clergy. Librarians do, too. The hard decisions were about bankers, finance types, and computer tech jobs. I see them as derived from manufacturers and merchants.
I will test this clustering against other theories to see if it is illuminating.