If you don't Mince Your Words you speak plainly, frankly and with brutal honesty. The phrase is always used in the negative - we never hear complaints of a person mincing their words. The first recorded use of the expression can be traced the mid 17th century. It takes it's meaning from the fact that butchers mince cheaper cuts of meat to make them easier to digest. Some things we are told are unpleasant to swallow and difficult to digest, and so a person "not mincing his words" is not making any effort to soften their message.