Sorrow of the Earthmother

Sorrow of the Earthmother is a part of tauren mythology. It is recorded in-game on a wall hanging in the Archdruid's tent in Thunder Bluff.

Speculation
It is possible that the "whispers from deep beneath the world" are the work of the Old Gods, who are often found in lore interfering with whispers that are able to drive people insane or warlike.