wane1
  
  v.
  - (of the moon) have a progressively smaller part of its visible surface illuminated, so that it seems to decrease in size.
 - become weaker.
 
 
  Phrase
  
    
      - on the wane
 becoming weaker or less vigorous. 
    
   
  Etymology
  OE wanian ‘lessen’, of Gmc origin; rel. to L. vanus ‘vain’.
 
  
    
wane2
  
  n.
 the amount by which a plank or log is bevelled or falls short of a squared shape.
 
  Derivative
  
  Etymology
  C17: from wane1.