kettle vs pen in

kettle

verb
  • Of a boiler: to make a whistling sound like the boiling of a kettle, indicative of various types of fault. 

  • To contain demonstrators in a confined area. 

noun
  • An instance of kettling; a group of protesters or rioters confined in a limited area. 

  • A vessel or appliance used to boil water for the preparation of hot beverages and other foodstuffs. 

  • A vessel for boiling a liquid or cooking food, usually metal and equipped with a lid. 

  • A kettle hole, sometimes any pothole. 

  • The quantity held by a kettle. 

  • A group of raptors riding a thermal, especially when migrating. 

  • A steam locomotive 

  • A kettledrum. 

pen in

verb
  • To cause to be stuck in a situation; to be forced into a situation by circumstances. 

  • To enclose (animals) in a pen. 

  • To schedule; fix a date for. 

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