This is a poem from "Crossing the Lingding Ocean" by Wen Tianxiang of the Song Dynasty. "Loyal heart" refers to a red and fiery heart. People who are loyal to the country are generally described as "blue-blooded red hearts." "History" refers to historical books. In ancient times, before the invention of paper, military and state affairs could only be recorded on bamboo slips. However, the water in the bamboo slips had to be evaporated with fire first, so that it would be convenient to write and prevent insects from being eaten. Later generations used this method. By extension, the classics recording history are collectively called "history".