Deep within the cavern, our shouts were met by a ghostly echo that seemed to come from all directions.

echo 是名词，意思是"回声"，指声音遇到障碍物后反射回来的现象。这个词来自希腊神话中的仙女Echo（厄科），她因受诅咒而只能重复别人话语的最后几个词。