a pig: the farmyard swine Israel was forbidden to eat, and also the wild boar of the forest
Hebrew uses one word for the animal, tame or wild. Most of the time it is the farmyard pig that Israel is told to leave alone. Once it is the wild boar that breaks into a vineyard and roots it up. English has to pick between "pig" and "boar" at each turn; Hebrew never has to.
Five of the seven times the word appears, the pig marks a boundary. Leviticus and Deuteronomy name it as the animal that looks like it should qualify, since its hoof is split, but fails the second test, since it does not bring food back up to chew again. So it stays off Israel's table. Isaiah then uses the word three times for people who have crossed that boundary deliberately, eating pig meat at meals held among the graves and pouring out pig blood as though it were a proper offering.
That history is why the word carries a charge that "pig" does not carry in English. This was not a neutral farm animal to mention in passing; naming it put you at the edge of everything Israel was told to keep clear of. The Greek Bible keeps the same edge: the ordinary word for a pig (χοῖρος) is what a Jewish son ends up feeding once he has fallen as far as he can fall, and a separate word for a sow (ὗς) drives a proverb about washing up only to go back to the mud.
The proverb about a gold ring in a pig's snout works from the same instinct. The point is not that pigs are dirty animals. It is that something genuinely valuable has been fastened to a creature that cannot appreciate it, so the beauty is wasted and the whole picture turns ridiculous.
Nuances
Disputed
Why the pig in particular is singled out as unclean, and therefore what weight the word carries in the food laws and in the prophets.
- majorityThe reason the text itself supplies: a clean land animal must both have a divided hoof and chew the cud, and the pig meets the first test but not the second, so it falls outside the ordered categories of the law and is excluded on formal grounds.; Mary Douglas, Purity and Danger (1966); Jacob Milgrom, Leviticus 1-16, Anchor Bible (1991); HALOT (Koehler-Baumgartner), s.v. חזיר
- minorityThe pig was shunned above all because of its use in the sacrificial rites of neighboring cults, especially rites addressed to the dead and to underworld powers, which is exactly the setting Isaiah gives it.; Roland de Vaux, "Les sacrifices de porcs en Palestine et dans l'Ancien Orient," in Bible et Orient (1967); G. Johannes Botterweck, "חזיר," in Theological Dictionary of the Old Testament (TDOT), vol. 4
- minorityThe avoidance is economic and ecological before it is theological: pig husbandry suits neither a herding economy nor the dry hill country, so the practice came first and the written rule ratified it.; Marvin Harris, Cows, Pigs, Wars, and Witches (1974); Brian Hesse, "Pig Lovers and Pig Haters: Patterns of Palestinian Pork Production," Journal of Ethnobiology 10 (1990)