ferment

Concise Oxford English Dictionary © 2008 Oxford University Press:
ferment

▶verb /fəˈmɛnt/ 

• 1 undergo or cause to undergo fermentation.

• 2 stir up (disorder).

▶noun /ˈfəːmɛnt/ 

• 1 agitation and social unrest.

• 2 dated a fermenting agent or enzyme.

– derivatives
fermentable adjective,
fermenter (US also fermentor) noun.

– origin ME: from OFr. ferment (n.), fermenter (v.), based on L. fermentum ‘yeast’, from fervere ‘to boil’.