Poosh

Poosh was a moon that had disappeared. Efforts to find the moon were unsuccessful, at least by the time the Tenth Doctor visited the planet of Midnight with Donna. Dee Dee Blasco had become a research assistant to Professor Hobbes on the strength of a paper she had written about Poosh. The timing and circumstances of Poosh's disappearance were not revealed to the Doctor. (DW: Midnight)
 * The script for Midnight is slightly vague about whether "Poosh" names the moon or the planet around which the moon orbits. Because the phrase "the lost moon of Poosh" is employed, It is possible to think of Poosh as the planet, and the moon being unnamed.  However, the Doctor proposes a toast to "Poosh" and Dee Dee accepts the toast without correction.  In the context of the conversation — during which the Doctor suggests that Dee Dee's contribution to science might be finding the lost moon — Poosh is more likely the moon's name, rather than the planet's.