dowse vs dowsing

dowse

verb
  • To use the dipping or divining rod, as in search of water, ore, etc. 

dowsing

noun
  • The practice of seeking water or other substances (usually liquid) with the aid of a forked stick or similar pointing device, as believed by some practitioners to derive from supernatural power. 

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