It's a common root in English, found in words like:
* Judge: The person who makes a judgment.
* Judgment: The act of judging or the result of judging.
* Judicial: Relating to the legal system and courts.
* Judiciary: The system of courts.
* Prejudice: Preconceived opinion or judgment.
* Adjudicate: To make a formal judgment.
Therefore, "jud" essentially conveys the idea of evaluating, deciding, or making a formal assessment.