Is it ensure, insure, or assure?
1620s, from Latin injunct-, past participle stem of injungere (see enjoin) + -ive. As a term in grammar, from 1910.
early 15c., from Late Latin injunctionem (nominative injunctio) "a command," noun of action from past participle stem of Latin injungere "impose," literally "attach to" (see enjoin).
A court order that either compels or restrains an act by an individual, organization, or government official. In labor–management relations, injunctions have been used to prevent workers from going on strike.