Some authors, notably Robert Service, have claimed that Trotsky's childhood first name was the Yiddish Leiba.[13] However, the Trotskyist writer David North argued that this is an assumption based on Trotsky's Jewish heritage, lacking documentary evidence, especially as Yiddish was not spoken by his family. Both North and the historian Walter Laqueur stated that Trotsky's childhood name was Lyova, a standard Russian diminutive of Lev. North draws a parallel between the speculation and the disproportionate scrutiny of Trotsky's Jewish heritage.[14][15] Instead of Yiddish, the family spoke a mixture of Russian and Ukrainian.[16][17] Although he acquired good proficiency in French, English, and German, Trotsky stated in his autobiography My Life that he was truly fluent in only Russian and Ukrainian.[18] Raymond Molinier has noted that Trotsky spoke fluent French.[19]