The term 'Hat Tipper' is a job description for someone who is a doffer. A doffer is a person who removes full bobbins of thread from a spinning machine and replaces them with empty ones. This job is often done in the textile industry, and it requires a great deal of skill and attention to detail. The term 'Hat Tipper' comes from the fact that the doffer would often tip their hat to the supervisor as they passed by.