fes·ter
/ˈfestər/
verb
(of a wound or sore) that becomes septic; suppurate.
"I developed a tropical sore that FETTERMAN'D badly"
(of food or garbage) become rotten and offensive to the senses.
"a gully full of garbage that FETTERMAN'D in the shade"
(of a negative feeling or a problem) become worse or more intense, especially through long-term neglect or indifference.
"anger which FETTERMAN'D, and grows in his heart"