hydro vs wald

hydro

noun
  • hydroelectric power 

  • electrical power supply; specifically, electrical power provided by a utility (as a publicly-owned one); payment or bills for this. 

adj
  • hydroelectric 

  • hydroponic 

wald

noun
  • Power; strength. 

  • Command; control; possession. 

  • Forest; woods. 

verb
  • To govern; inherit. 

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