Is it ensure, insure, or assure?
late 14c., "to decide, resolve; to arrange the time of (a meeting, etc.)," from Anglo-French appointer, Old French apointier "make ready, arrange, settle, place" (12c.), from apointer "duly, fitly," from phrase à point "to the point," from a- "to" (see ad-) + point "point," from Latin punctum (see point (n.)). The ground sense is "to come to a point (about some matter)," therefore "agree, settle." Meaning "put (someone) in charge" is early 15c. Related: Appointed; appointing.