Is it ensure, insure, or assure?
headache head·ache (hěd'āk')
A pain in the head. Also called cephalalgia.
Pain in the head, caused by stimulation of or pressure to any of various structures of the head, such as tissue covering the cranium, cranial nerves, or blood vessels. Headache can be a primary disorder, as in migraine or cluster headaches, or a common symptom associated with head injury or many illnesses such as acute infection, brain tumor or abscess, eye disorders such as glaucoma, dental disease, and hypertension. See also cluster headache, migraine.
Any trouble, annoyance, vexation, etc: another headache for pro coaches (1934+)