In ancient Greece, an archaic wooden image used in cult worship, such as a statue of Athena or Hermes. It was the xoana, not the more showy chryselephantine statues, that were the true foci of worship. The Erechtheum in Athens held the palladium, the xoanon of Pallas Athena.
They were traditionally said to have fallen from the heavens. However, consulting a Greek dictionary I find xoanopoiía 'carving of images' and xoís 'chisel' from the verb xéo 'scrape, carve, work', so I think they probably helped them along quite a bit. In this fallen sense the meteoric stone equivalent is the baetyl.
Also a word used in a Doctor Who episode for the mere sound of it, and spelled with a Z.