Elizabeth Starr Masoudnia, Philadelphia Orchestra English Horn, is profiled by Susan Lewis of radio station WRTI.
You can read the full article, and listen to an audio interview here.
Masoudnia says it's "an extremely expressive instrument, and so composers use it usually when they have something very special to express." Wagner, Strauss, and Mahler are among other major composers who have written notable solos for the instrument.
As for the name? Likely a mistranslation. Masoudnia explains: "In German, it was called angelish horn—or horn of the angels—and the French word for it is cor anglai, which meant angled horn."
In the orchestra, the English horn player sits with the oboes, and is often called on to play both instruments.