Is it ensure, insure, or assure?
late 14c., "assign, bestow," from Latin attributus, past participle of attribuere "assign to, add, bestow;" figuratively "to attribute, ascribe, impute," from ad- "to" + tribuere "assign, give, bestow" (see tribute). Related: Attributed; attributing.
"quality ascribed to someone," late 14c., from Latin attributum "anything attributed," noun use of neuter of attributus (see attribute (v.)). Distinguished from the verb by pronunciation.