fiddle with vs weaken

fiddle with

verb
  • To adjust the position, as of an electronic device, in order to provide better reception or signal. 

  • To manipulate an object, especially in a nervous or restless manner. 

  • To manipulate in order to gain something for oneself. 

weaken

verb
  • To make weaker or less strong. 

  • To become weaker or less strong. 

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