Is it ensure, insure, or assure?
late 14c., "schoolmaster, teacher," from Old French pedagoge "teacher of children" (14c.), from Latin paedagogus, from Greek paidagogos "slave who escorts boys to school and generally supervises them," later "a teacher," from pais (genitive paidos) "child" (see pedo-) + agogos "leader," from agein "to lead" (see act (n.)). Hostile implications in the word are at least from the time of Pepys (1650s). Related: Pedagogal.