Lewis & Short

Popĭlĭus (Popill-), i, m., and Popi-lĭa (Popill-), ae, f.,

  1. I. the name of a Roman gens. So esp.,
      1. 1. M. Popillius Laenas, a consul A. U.C. 395, Cic. Brut. 14, 56.
      2. 2. C. Popilius Laenas, the assassin of Cicero, Liv. Epit. 120; Sen. Suas. 7.
      3. 3. In fem.: Popilia, the wife of Q. Catulus, Cic. de Or. 2, 11, 44.
        Hence,
  2. II. Popĭlĭus, a, um, adj., of or belonging to a Popilius, Popilian: gens, Cic. Leg. 2, 22, 55.