Is it ensure, insure, or assure?
1681, from Medieval Latin spasmodicus, from Greek spasmodes "of the nature of a spasm," from spasmos (see spasm) + -odes "like."
spasmodic spas·mod·ic (spāz-mŏd'ĭk)adj.
Relating to, affected by, or having the character of a spasm; convulsive.
Happening intermittently; fitful.
Given to sudden outbursts of energy or of feeling; excitable.