Diabetes comes from the Greek word for siphon. A siphon is a tube that carries large quantities of water. With respect ot people it refers to the fact that untreated diabetes often results in the passage of large quantities of urine.
It became known that there were two main types of patients that passed large amounts of water, those who passed sweet urine and those that passed bitter urine. Those that passed sweet urine were termed `mellitus' and those that passed bitter urine `insipidus'. Thus the two main types of diabetes are Diabetes Mellitus and Diabetes Insipidus.