C.F.
In our experience at Countryside Montessori, usually they are teething or getting more social and need help learning what to say. We shadow them, ,stop them with a louder firmer voice than normal, then in a regular voice tell them what to do or say. Give the teethers a teething ring. If you do this each time, they usuaaly stop. If not try time out. ALSO make sure no one plays biting games such as animals, the gonna get your fingers game and such.