Webster's Revised Unabridged Dictionary · 1913

Whom

Whom , pronoun

[Old English wham, Anglo-Saxon dative hwām, hw{not transcribed}m. See Who.]

The objective case of who. See Who.
And every grass that groweth upon root She shall eke know, and whom it will do boot. — Chaucer

In Old English, whom was also commonly used as a dative. Compare Him.