Mistress Cassandra wanted her slave to learn that she was not happy with him. She had a sweet face and even when she is mad, she looks like she is not serious about it. So she did it practically to show the guy how disappointed to him. The mistress used a banana to tell him what she wanted to do to him. So she crushed the banana and asked him to lick it from her feet if he wanted to avoid being trampled cruelly.