The answer to your question would be that the suffix identified in the word "inspector" is the following one: -or. This is a suffix which is used as a variation of the suffix -er which refers to someone who performs a certain action, that is, it refers to "one who does x". Yet, at the same, it has its own meaning which has to do with a person that<u> is </u>something. Other examples of this suffix are distributor, investigator, and translator. As you can see, a translator is someone who translates, a distributor is someone who distributes and an investigator is someone who investigates. Therefore, an inspector is someone who inspects.
