caution (n.) Look up caution at Dictionary.com
c.1300, "bail, guarantee, pledge," from O.Fr., "security, surety," from L. cautionem (nom. cautio), from cautus pp. of cavere "to be on one's guard" (see caveat). The Latin sense re-emerged in Eng. 16c.-17c. The verb sense of "to warn" is from 1640s.