Geoff, other shadings of both the adj. and n. are nothing new. referring to means of livelihood and to non-amateurs in sports, for instance, both trace to the 1800s. disparaging usage also shows up in this period. 1887 Pall Mall G. 11 Feb. 4/2 Ladies raised+to the now extinct position of ‘professional beauty’. [extinct??] 1879 Cornh. Mag. Oct. 414 It is one of the misfortunes of the professional Don Juan that his honour forbids him to refuse battle.
I was surprised to learn that the first attested sense of profession/professional pertains to entrance into a religious order. I can quote chapter and verse of all senses if you like....