The Hebrew verb nabach means to bark, as a dog does. It is an onomatopoetic word that imitates the sound of a dog barking. The word appears only once in the Old Testament, in Isaiah's vivid prophetic imagery describing Israel's negligent watchmen.
In Isaiah 56:10, Israel's watchmen (spiritual leaders) are compared to mute dogs that cannot bark. The prophetic imagery is devastating — watchdogs that fail to bark are useless, just as spiritual leaders who fail to warn the people of danger have abdicated their calling. This word thus carries significant weight in prophetic criticism of unfaithful leadership, a theme that resonates throughout the prophetic books.