Albert Barnes Commentary 2 Samuel 9:8

"And he did obeisance, and said, What is thy servant, that thou shouldest look upon such a dead dog as I am?" — 2 Samuel 9:8 (ASV)

Mephibosheth’s humility of expression, even in the mouth of an Easterner, is painful. It was perhaps in part the result of his helpless lameness and the other misfortunes of his life.

A dead dog - The wild dogs of the East, which still abound in every town, are the natural objects of contempt and dislike.