The article marks the special servant; the body-servant.
Ear (ὠτίον)
A diminutive in form but not in sense; according to a Greek popular usage which expressed parts of the body by diminutives; as ῥίνια, the nostrils; ὀμμάτιον, the eye; σαρκίον, the body. Peter aimed his blow at the servant's head, but missed.