This is a euphemism for Hanging one's self. This is based off of a rather humorous scene in the anime "Sayonara Zetsubou Sensei," Where the titular character, literally named "Despair" in Japanese, tries to hang himself before a cheerful and exceedingly optimistic girl by the name of "Kafuka Fuura," who states that her mother, father and many people in her family have tried to "Make themselves taller."