shoofly vs slewfoot

shoofly

noun
  • A device for throwing the track temporarily to one side for carrying out repairs, etc. 

  • A child's rocker having a seat supported between two boards cut and painted to resemble animals. 

  • A police officer assigned to keep tabs on other members of the police. 

slewfoot

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