big cheese, the

The  boss,  an  important  person;  also,  a  self-important person. This term is a slangy Americanism dating from the late nineteenth century, and its etymology is disputed. Some believe it comes from the Per- sian or Urdu word chiz or cheez for “thing”; others believe it is simply a play on the English word chief. There are several synonymous usages, among them big gun, big shot, and big wheel. The first dates from the 1830s. An 1834 citation has  it, “The  big  guns  of  the  nation  are  there  [in Washington].”  The  last  two expressions both date from the 1930s.