We often meet people who are hesitant to say what is on their mind. When something unpleasant happens, they refuse to speak plainly or openly about the matter. When you say that someone is `mealy mouthed', what you mean is that the individual is not frank or sincere. He is not brave enough or honest enough to speak his mind. The term is normally used to show contempt for an individual.

Jai is a young, mealy-mouthed politician that people just love to hate.

Food that is dry and powdery is often referred to as being `mealy'. So, when you say that someone is `mealy-mouthed', what you mean is that the person has something dry and powdery in his mouth. He is therefore unable to speak clearly. According to scholars, the expression comes from the German `Mehl im Maule behalten', meaning `to carry a meal in the mouth'.