When did "philosopher" become a label with a positive valence?

That's an important question, when one reads that a "celebrity" charlatan philosopher (not Zizek, but close) has endorsed a certain view.  (Thanks to James O'Connor for the pointer.)  This is really a question for a sociologist or other empirical scholar of the humanities who can tell us when "philosopher" became an honorific and why.  I suspect it is due to the historical connection between "philosophy" and both "science" and "theology," but I would be curious to get references from knowledgeable readers.