"arena :: Arena (n.) Sand or gravel in the kidneys..
Arena :: Arena (n.) The area in the central part of an amphitheater, in which the gladiators fought and other shows were exhibited; -- so called because it was covered with sand..
Arena :: Arena (n.) Any place of public contest or exertion; any sphere of action; as, the arenaof debate; the arena of life..
Arenaceous :: Arenaceous (a.) Sandy or consisting largely of sand; of the nature of sand; easily disintegrating into sand; friable; as, arenaceous limestone..