Where does “зенитный” come from?

зенитный (Russian) comes from Russian зени́т, from French zénith, from Middle French zenith, from Old French cenit, from Medieval Latin cenit, from Arabic سَمْت, from Aramaic סֵימִטָא, from Latin sēmita.

зенитный (Russian): zenith; zenithal; antiaircraft / anti-aircraft