c. 1300, caucioun, "bail, guarantee, pledge," from Old French caution "security, surety" (13c.), from Latin cautionem (nominative cautio) "caution, care, foresight, precaution," noun of action from past-participle stem of cavere "to be on one's guard" (from PIE root *keu- "to see, observe, perceive").
The Latin sense re-emerged in English as "prudence in regard to danger" (1650s). The meaning "word of warning, monitory advice" is from c. 1600. The meaning "anything which excites alarm or astonishment" is U.S. slang, 1835.
"previous caution, prudent foresight (to prevent mischief or secure good results); a measure taken beforehand, an act of foresight," c. 1600, from French précaution (16c.) and directly from Late Latin praecautionem (nominative praecautio) "a safeguarding," noun of action from past-participle stem of Latin praecavere "to guard against beforehand," from prae "before" (see pre-) + cavere "to be one's own guard" (see caution (n.)). In mid-20c. a euphemism for "contraception." The verb meaning "to warn (someone) in advance" is from c. 1700.
"warning, hint of caution," 1550s, Latin, literally "let him beware," third person singular present subjunctive of cavere "to beware, take heed, watch, guard against" (from PIE root *keu- "to see, observe, perceive"). The legal meaning "public warning preventing some action" is attested from 1650s.
c. 1400, monicioun, "warning, instruction given by way of caution," from Old French monition (13c.) and directly from Latin monitionem (nominative monitio) "warning, admonition, reminding," noun of action from past-participle stem of monere "to admonish, warn, advise," from PIE *moneie- "to make think of, remind," suffixed (causative) form of root *men- (1) "to think." With specific meanings in civil and ecclesiastical law.