Webster's Revised Unabridged Dictionary · 1913

Warn

Warn (warn) , transitive verb

[Old English wernen, Anglo-Saxon weornan, wyrnan. Compare Warn to admonish.]

To refuse. [Obsolete] — Chaucer

Warn , transitive verb

[Old English warnen, warnien, Anglo-Saxon warnian, wearnian, to take heed, to warn; akin to Anglo-Saxon wearn denial, refusal, Old Saxon warning, wernian, to refuse, Old High German warnen, German warnen to warn, OFries. warna, werna, Icelandic varna to refuse; and probably to English wary. {not transcribed}.]

1.
To make ware or aware; to give previous information to; to give notice to; to notify; to admonish; hence, to notify or summon by authority; as, to warn a town meeting; to warn a tenant to quit a house.
Warned of the ensuing fight. — Dryden
Cornelius the centurion... was warned from God by an holy angel to send for thee. — Acts x. 22
Who is it that hath warned us to the walls? — Shakespeare
2.
To give notice to, of approaching or probable danger or evil; to caution against anything that may prove injurious.
Juturna warns the Daunian chief of Lausus' danger, urging swift relief. — Dryden
3.
To ward off. [Obsolete] — Spenser