Kashrut
Among the numerous laws that form "kashrut" are prohibitions on the consumption of certain animals (such as pork and shellfish), mixtures of meat and milk, and the commandment to slaughter mammals and birds according to a process known as "shechita". There are also laws regarding agricultural produce that might impact the suitability of food for consumption.
History of vegetarianism
In Greek-Orthodox Christianity (Greece, Cyprus, Russia, Serbia and other Orthodox countries), adherents eat a diet completely free of animal products for fasting periods (except for honey) as well as all types of oil and alcohol, during a strict fasting period. The Ethiopian Orthodox Church prescribes a number of fasting (tsom, Ge'ez: ጾም ṣōm, excluding any kind of animal products, including dairy products and eggs) periods, including Wednesdays, Fridays, and the entire Lenten season, so Ethiopian cuisine contains many dishes that are vegan.