Mark Twain provided humorously telling evidence for the frequent unreliability of back-translation when he issued his own back-translation of a French translation of his short story, "The Celebrated Jumping Frog of Calaveras County". He published his back-translation in a 1903 volume together with his English-language original, the French translation, and a "Private History of the 'Jumping Frog' Story". The latter included a synopsized adaptation of his story that Twain stated had appeared, unattributed to Twain, in a Professor Sidgwick’s Greek Prose Composition (p. 116) under the title, "The Athenian and the Frog"; the adaptation had for a time been taken for an independent ancient Greek precursor to Twain's "Jumping Frog" story.
What language did Twain remove a back-translation?