Katz is a common German Ashkenazi Jewish surname.
Germans with the last name Katz may originate in the Rhine River region of Germany, where the Katz Castle is located. (The name of the castle does not derive from Katze, "cat", but from Katzenelnbogen, going back to Latin Cattimelibocus, consisting of the ancient Germanic tribal names of the Chatti and Melibokus.)
Where it is a Jewish surname, Katz or Katzenellenbogen is almost always a Hebrew abbreviation (Hebrew: כּ״ץ, Kaf (a) Tzaddi, or Ka-Tz) formed from the initials of the term Kohen Tzedek ("priest of justice", "authentic priest"), indicating descent from Jewish priests (although not all Jewish Katzes are in fact descended from priests).[citation needed]
The full form Kohen Tzedek appears as a surname or title in a number of medieval sources,[1] while the acronym Katz has been used since the seventeenth century, or perhaps somewhat earlier. The expression may be derived from Melchizedek ("king of righteousness"), who is called "the priest of the most high God" (Genesis 14:18), or perhaps from Psalms 132:9: "Let thy priests be clothed with righteousness (tzedeq)".
If the reading is correct, this abbreviation occurs on a tombstone, dated 1536, in the cemetery of Prague.[2] It is found also on a tombstone of the year 1618 in Frankfurt,[3] in the books of the Soncino family of Prague of the seventeenth century,[4] and in one of the prefaces to Shabbethai ben Meïr ha-Kohen's notes on the Choshen Mishpat (Amsterdam, 1663).
The use of the abbreviated and Germanicized Katz likely coincided with the imposition of German names on Jews in Germany in the 18th and 19th centuries. Jews with the surname Katzenelenbogen may also have shortened their surname to Katz upon arrival in America.[citation needed]