Parasite : comes from the Greek para, "beside" and sitos, "grain or food." Together parasitos originally meant "fellow guest." It came to mean in ancient Greece a professional dinner guest who was invited to amuse or flatter the host. By the 1500s, the meaning had expanded to "a person who takes advantage of others," which today could still be by eating often at someone's house and not returning the favor.
Salary : derives from Latin word salarium, which refer to allowance given to soldiers to buy salt.