2 Samuel 18:21

Cushi . This is not a proper name, but signifies that he was an Ethiopian, that is, a negro slave in Joab's service. Joab was unwilling to expose Ahimaaz to me king's displeasure, and we gather from 2 Samuel 18:27 that the sending of a person of low rank would be understood to signify evil tidings. The bearer of good news received a present, and therefore the passing over all Joab's personal friends to send a slave was proof that the message was not expected to bring the bearer honour or reward. And Joab was quite right in supposing that David would be more displeased at his son's death than pleased at the victory.