interfere vs spur on

interfere

verb
  • To get involved or involve oneself, causing disturbance. 

  • To sexually molest, especially of a child. 

  • (of waves) To be correlated with each other when overlapped or superposed. 

  • To strike one foot against the opposite foot or ankle in using the legs. 

spur on

verb
  • To spur or urge (someone) to do something. 

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