the dog: a scavenging and largely despised animal of the biblical world, and by extension a byword for a worthless or contemptible person
In the Bible the dog is almost never a pet. It is a scavenger that prowls the town at night, laps water from puddles, and feeds on the bodies of the dead. Because of this, to be eaten by dogs or left for dogs is one of the grimmest fates a person can suffer, and the greedy, prowling dog becomes a ready image for enemies and for shameless appetite.
From that lowly picture grows a second use: to call a person a dog, or a dead dog, is to put them at the very bottom. Sometimes it is contempt hurled at an enemy, and sometimes it is a speaker humbling himself before a king, as when David and Mephibosheth each ask why anyone should bother with a mere dead dog. The word itself does not change meaning; the same despised animal simply stands for the despised or lowly person.
One law uses the word in a more pointed way still. Deuteronomy forbids bringing the wages of a dog into the temple alongside the hire of a prostitute, and most readers take the dog there as a blunt term for a male prostitute. That reading, and the question of whether it points to an organized temple prostitution, is taken up in the scholarship note below.
Nuances
Whether "the wages of a dog" in Deuteronomy 23:18, taken as the earnings of a male prostitute, reflects an organized sacred or cult prostitution attached to a temple.
- minorityIt reflects a Canaanite-style cult or temple prostitution that the law is excluding from the sanctuary; the "dog" is a male sacred prostitute.; BDB, s.v. כֶּלֶב
- majorityIt names a male prostitute in ordinary, contemptuous terms; the older reconstruction of an organized sacred-prostitution institution behind such texts is doubtful and widely questioned.; Jeffrey H. Tigay, Deuteronomy (JPS Torah Commentary)