A lazy Susan is a turntable (rotating tray) placed on a table or countertop to aid in distributing food. It is likely that the explanation of the term "lazy Susan" has been lost to history. Folk etymologies claim it as an American invention. According to lore, Thomas Jefferson invented the device, which was known as a "dumbwaiter", for his daughter Susan. Regardless of the origins of the name, by 1917 it was advertised in Vanity Fair as "Ovington's $8.50 mahogany 'Revolving Server or Lazy Susan'", but the term's use predates both the advertisement and, probably, the country.

Source: Wikipedia