When speaking Russian to her he called her 'thou,' and that always irritated her. [In Russian as in French and other languages the second person singular is used in conversation between intimates and also in speaking to inferiors.]
Cuando Karenin hablaba en ruso y la trataba de tú, este «tú» producía en Ana un irresistible sentimiento de irritación. –Agradezco mucho tu decisión.