fell2
  
  v.
  - cut down (a tree). 
▸knock down.
 - 
(also flat-fell)
 stitch down (the edge of a seam) to lie flat.
 
n.
 an amount of wood cut.
 
  Derivative
  
  Etymology
  OE fellan, of Gmc origin; rel. to fall.
 
  
    
fell3
  
  n.
 a hill or stretch of high moorland, especially in northern England.
 
  Etymology
  ME: from ON fjall, fell ‘hill’.
 
  
    
fell4
  
  adj.
 literary of terrible evil or ferocity.
 
  Phrase
  
    
      - in 
(or at)
 one fell swoop
 all in one go. 
[from Shakespeare's Macbeth (iv. iii. 219).]
 
    
   
  Etymology
  ME: from OFr. fel, nominative of felon (see felon1).
 
  
    
fell5
  
  n.
 archaic an animal's hide or skin with its hair.
 
  Etymology
  OE fel, fell, of Gmc origin.