Lewis & Short

părĭĕtārĭus, a, um, adj. [paries],

  1. I. of or belonging to walls: structor, Firm. Math. 8, 24; Inscr. Rein. cl. 11, n. 112: pictor, Edict. Diocl. p. 19.
  2. II. Subst.: părĭĕ-tārĭa, ae, f., the herb pellitory or parietary: herbam perdicalem Latini muralem et parietariam, alii vitriariam appellant, App. Herb. 81.
    Acc. to Aur. Vict. Epit. 41, Constantine the Great bestowed on the emperor Trajan, on account of the numerous inscriptions which he had caused to be placed on buildings, the sobriquet of herba parietaria (Amm. 27, 3, 7, has instead, herba parietina).