penny whistle vs whistler

penny whistle

noun
  • A tin whistle. 

whistler

noun
  • Someone or something that whistles, or who plays a whistle as a musical instrument. 

  • The mountain beaver (Aplodontia rufa). 

  • The goldeneye (certain ducks of genus Bucephala). 

  • The whistling marmot (Marmota caligata). 

  • An audio-frequency electromagnetic wave produced by atmospheric disturbances such as lightning. 

  • A broken-winded horse. 

  • Any of several passerine birds of the genera Pachycephala and Coracornis, of Australasia and the western Pacific. 

  • Any bird that whistles or is noted for its whistling vocalisations (applied regionally to various specific species). 

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