Celtic was a language spoken by the Celt people of Great Britain. When the Tenth Doctor and English-speaking Donna Noble arrived in Pompeii, Donna wondered what would happen if she spoke Latin to the locals, whose native language was Latin. Instead of hearing Latin, because of the TARDIS translation circuits, a Stallholder believed her to be Celtic. Upon hearing the Doctor speak Latin, Lobus Caecilius and Lucius Petrus Dextrus believed him to be Celtic as well. (TV: The Fires of Pompeii) Similarily, Winston Churchill was heard to be speaking Celtic by a Roman soldier in ancient Britain when he addressed him in Latin. (AUDIO: Living History)