Why are some job titles ending in er others in or?

Job titles ending in "er" typically denote someone who performs an action or activity, such as "teacher" or "driver." In contrast, titles ending in "or" often originate from Latin and refer to someone who holds a position or role, such as "doctor" or "actor." The distinction often reflects the etymological roots of the Words, with "er" being more commonly used in English, while "or" is more prevalent in formal or academic contexts.