E. Cobham Brewer 18101897. Dictionary of Phrase and Fable. 1898.
Ring in the Ear.
A sign of slavery or life-long servitude.
Then Eldad took an awl, and, piercing his [Jeturs] ears against the doorpost, made him his servant for ever. The elders pronounced a blessing, and Eldad put a ring through the ears of Jetur, as a sign that he was become his property.Eldad the Pilgrim, chap. i.