Etymologically,
Moral < Moralis (L) = pertaining to Mores (L) = customs, including both personal habits and societal norms
Ethics < Ethica (Gk) = also means customs, including both personal habits and societal norms, but is usually meant as a short form of Ethica Arete = GOOD habits
Justice < Iustitia (L) < Ius (L) - Universal, Natural Law.
Well, ok, Ius was also often used to mean "common law" derived from Jurisprudence (as opposed to Lex, codified law passed by the decree of a king or legislature), which is based on tradition and societal norms and thus morality. However, I prefer its usage, as a synonym with Fas (L) = absolute, Divine Law; the Will of God.