In culinary terminology, squab is an immature domestic pigeon, typically under four weeks old, or its meat. The meat is widely described as tasting like dark chicken. The term is probably of Scandinavian origin; the Swedish word skvabb means "loose, fat flesh". It formerly applied to all dove and pigeon species, such as the wood pigeon, the mourning dove, the extinct-in-the-wild socorro dove, and the now extinct passenger pigeon, and their meat. More recently, squab meat comes almost entirely from domesticated pigeons. The meat of dove and pigeon gamebirds hunted primarily for sport is rarely called squab. The practice of domesticating pigeons as livestock may have come from North Africa; historically, squabs or pigeons have been consumed in many civilizations, including ancient Egypt (still common in modern Egypt), Rome, China, India (Northeast), and medieval Europe. Although squab has been consumed throughout much of recorded history, it is generally regarded as exotic, not as a contemporary staple food; there are more records of its preparation for the wealthy than for the poor. The modern squab industry uses utility pigeons. Squabs are raised until they are roughly a month old, when they reach adult size but have not yet flown, before being slaughtered. The practice of domesticating pigeon as livestock may have come from the North Africa; historically, squabs or pigeons have been consumed in many civilizations, including ancient Egypt, ancient Rome, and Medieval Europe. Doves are considered kosher, though are not as common in the Jewish diet as they were in ancient times. Texts about methods of raising pigeons for their meat date as far back as AD 60 in Spain. Such birds were hunted for their meat because it was a cheap and readily available source of protein. In the Tierra de Campos, a resource-poor region of north-western Spain, squab meat was an important supplement to grain crops from at least Roman times. Caelius Aurelianus, an Ancient Roman physician, regarded the meat as a cure for headaches, but by the 16th century, squab was believed to cause headaches.