The meaning of Kosher is correct or acceptable, and with that meaning informally entered the English language.
But the origin of Kosher laws is in the Bible, and in Talmud and other codes of Jewish traditions are elaborate. They have been applied for varying conditions for centuries, and these rules, both ancient and modern, govern the OKS Kosher certification.
The Bible lists the basic categories of foods that are not kosher. These include some animals, birds and fish (such as pig and rabbit, eagle and owl, catfish and sturgeon), most insects and any conch or reptiles.