When some people in ancient cultures saw a lunar eclipse, they literally believed that the red color was blood. Here are two articles which reference this:
http://www.space.com/scienceastronomy/solarsystem/lunar_lore_000118.html
http://msnbc.msn.com/id/3404517/
If you don't want to read the articles, here are two excerpts from them, listed respectively.
"The dark-blood color of most lunar eclipses bolsters the idea that the Moon is being eaten, with "blood" spreading across its face."
"Some believed a dragon of the sky was eating the moon, flooding it with blood before consuming it entirely."
Or, you can look in the bible:
Joel 2:31 : "The sun will be turned to darkness and the moon to blood before the great and dreadful day of the Lord"
That passage references both a solar and a lunar eclipse, both of which caused great fright among ancient people, often seen as bad omens.
Just because you haven't heard of something doesn't mean that it doesn't exist.