Is it ensure, insure, or assure?
1620s, "act of fixing or steadying;" from settle (v.) + -ment. Meaning "a colony," especially a new one, "tract of country newly developed" is attested from 1690s; that of "small village on the frontier" is from 1827, American English. Sense of "payment of an account" is from 1729; legal sense "a settling of arrangements" (of divorce, property transfer, etc.) is from 1670s.