Tristan und Isolde is an 1865 opera by Richard Wagner about the ill-fated affair between the knight Tristan and the lady Isolde. The opera is based on a medieval romance that was absorbed into the Arthurian tradition. The quoted scene occurs near the beginning of the opera, with Tristan escorting the captured Isolde by ship to Cornwall.
Le Galliene translates the quoted lines:
Eliot quotes form Tristan und Isolde again in line 42: