Celtic (language)

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, a Stallholder believed her to be Celtic. Upon hear the Doctor speak Latin, Lobus Caecilius believed him to be Celtic as well. (TV: The Fires of Pompeii)