before 1000;Middle Englishwarnen,Old Englishwarnian; cognate with Germanwarnen. Cf. ware2
prewarn, verb (used with object)
rewarn, verb (used with object)
1. forewarn. Warn, caution, admonish imply attempting to prevent another from running into danger or getting into unpleasant or undesirable circumstances. To warn is to speak plainly and usually in strong terms: to warn him about danger and possible penalties. To caution is to advise about necessary precautions, to put one on one's guard about possibly harmful circumstances or conditions, thus emphasizing avoidance of undesirable consequences: to caution him against driving in such weather. Admonish suggests giving earnest, authoritative advice with only tacit references to danger or penalty: to admonish a person for neglecting his duties.
O.E. warnian "to give notice of impending danger," also intrans., "to take heed," from W.Gmc. *warnojanan (cf. O.N. varna "to admonish," O.H.G. warnon "to take heed," Ger. warnen "to warn"); related to O.E. wær "aware, cautious" (see wary).