v.
 
[
often as adj. festering]
   
- (of a wound or sore) become septic. 
▸(of food or rubbish) become rotten.
 - (of a negative feeling or a problem) intensify, especially through neglect.
 - deteriorate physically and mentally in isolated inactivity.
 
 
  Etymology
  ME: from fester ‘fistula’, later ‘festering sore’, or OFr. festrir (v.), both from OFr. festre (n.), from L. fistula ‘reed, fistula’.