a person who must work hard and long at unpleasant or uninteresting task

slave, very hard worker

an old horse; a person paid to do hard and uninteresting work as a writer

person who does easy work for money

a kind of small animal with a soft body, no limbs and a shell on its back

laggard

a person who finds it difficult to stop working, e.g. a business person, writer, researcher

slave, very hard worker