circus ring vs doughnut

circus ring

noun
  • A circular arena in a circus, where the acts are performed. 

doughnut

noun
  • A toroidal vacuum chamber. 

  • A deep-fried piece of dough or batter, commonly of a toroidal (a ring doughnut) shape, often mixed with various sweeteners and flavourings; or flattened sphere (a filled doughnut) shape filled with jam, custard or cream. 

  • A peel-out or skid mark in the shape of a circle; a 360-degree skid. 

  • A spare car tyre, usually stored in the boot, that is smaller than a full-sized tyre and is only intended for temporary use. 

  • A kind of tyre for an airplane. 

  • A vulva; (by extension) a woman's virginity. 

  • A foolish or stupid person. 

  • A circular life raft. 

How often have the words circus ring and doughnut occurred in a corpus of books? (source: Google Ngram Viewer )