If your excuses for not finishing your homework range from acid rain to your dog eating it, your teacher may accuse you of being mealymouthed, i.e., not speaking frankly.
When an apple or a peach is mealy, its texture has turned to mush — like bread, which is made from meal. No one likes to get a mouthful of that kind of apple or peach, and no one likes listening to someone who is mealymouthed either. To be mealymouthed is to be indirect and a tad sleazy.