Dona nobis pacem (Latin for "Grant us peace") is a phrase in the Agnus Dei section of the Roman Catholicmass. The phrase, in isolation, has been appropriated for a number of works, which include:
The phrase is used by the Doctor - season 4, episode 6 of Doctor Who, The Poison Sky - when speaking in code to Donna Noble who is trapped on the TARDIS by the Sontarans. (Original airdate: 3 May 2008)