Diabetes insipidus (DI) is completely different from diabetes mellitus. Both were named many centuries ago when there was very little known about these two conditions. Diabetes is an ancient medical word akin to a siphon so that if you are missing the pituitary/hypothalamic water control factors (vasopressin), water would pour out of your body uncontrollably. There are types of DI in which vasopressin is no longer available, and other types in which the kidneys do not respond to available hormones. Insipidus means unknown type so that DI was an outpouring of water for unknown reasons when originally named.
Diabetes mellitus comes from a combination of the excess urination and the fact that the urine was like honey (it was sweet, and attracted ants) from the sugar losses occurring from insufficient insulin of several types.
DI should be relatively easy to control with vasopressin replacement either in nasal spray or tablet form under most circumstances.
SB
