To draw a modern analogy if an occupation is a service industry, it's probably a Profession skill.

While a Craft skill represents ability in creating or making an item, a Profession skill represents an aptitude in a vocation requiring a broader range of less specific knowledge. You could have several Profession skills, each with its own ranks, each purchased as a separate skill. Your ranks in that skill don't affect any Profession (miller) or Profession (miner) checks you might make. For instance, you could have the skill Profession (cook).

Like Craft, Knowledge, and Perform, Profession is actually a number of separate skills. You are trained in a livelihood or a professional role, such as apothecary, boater, bookkeeper, brewer, cook, driver, farmer, fisher, guide, herbalist, herder, hunter, innkeeper, lumberjack, miller, miner, porter, rancher, sailor, scribe, siege engineer, stablehand, tanner, teamster, woodcutter, or the like.