jag1
  
  v.
 (jags, jagging, jagged)
 stab, pierce, or prick.
n.
  - a sharp projection.
 - chiefly Scottish an injection.
 
 
  Derivative
  
  Etymology
  ME: perh. symbolic of sudden movement or unevenness (cf. jam1 and rag1).
 
  
    
jag2
  
  n.
  - informal, chiefly N. Amer. a bout of unrestrained activity or emotion:
 a crying jag.
 - dialect a bundle.
 
 
  Etymology
  C16 (in sense ‘a load of hay or wood’, later ‘as much alcohol as one can hold’): of unknown origin.