1896, coined 1893 in German from Greek hypo- "under" (see sub-) + thalamus "part of the brain where a nerve emerges."
hypothalamus hy·po·thal·a·mus (hī'pō-thāl'ə-məs)
n.
The part of the brain that lies below the thalamus, forming the major portion of the ventral region of the diencephalon, and that regulates bodily temperature, certain metabolic processes, and other autonomic activities.
The part of the brain that controls hunger, thirst, and body temperature and regulates various activities in the body connected with metabolism, including the maintaining of water balance. The hypothalamus also controls the action of the pituitary gland.