Esperanto
From Tardis Wiki, the free Doctor Who reference
Esperanto was a language invented by Polish oculist Zamenhof in 1887. He intended it to be the universal language of peace.
The Master once went under the alias "Estro"; an Esperanto word for "Master". The Eighth Doctor reflected that it was typical of the Master to corrupt something intended for good. (EDA: Legacy of the Daleks)
The idea of a universal language like Esperanto was not exclusive to Earth. For example, the Fourth Doctor once called Trillic "a sort of cybernetic Esperanto". (TVC: The Wreckers)
