When we say that a person is six feet under, this means that he or she is dead and buried. Some historians believe that this slang expression has historical significance related to The Great Plague of London in 1665. In order to prevent further outbreak, six feet may have been the minimum depth to bury dead bodies. If you hear that a person has gone to meet one’s maker, checked out, or is pushing up daisies this also means that he is dead. These are slang expressions that are typically used between close friends in informal situations. To be more respectful, you should say that a person is gone, deceased, departed, or no longer with us.