You know what's a funny word? Bulwark. According to dictionary.com, bulwark means "to serve as a bulwark." Okay, so the verb part of the definition doesn't help. But the noun part does. Bulwark means "a person, thing, or concept that is a defense or protection."
To be honest, I don't trust the dictionary. Listen to the word: "bulwark." It sounds like some sort of beast, perhaps mythical. I can't decide if the bulwark can fly or not. He is certainly carnivorous. But then it occurred to me. The dictionary gives the modern definition, but doesn't give the word origin. The origin must be something like this:
In ancient times, the mighty bulwark roamed the Earth, terrorizing villages in search for flesh. Eventually, man domesticated the beast, and the bulwark served as a sentinel, or watchdog, for the village, keeping it safe from animal attack or enemy towns. Hence, the term "bulwark" has come to mean something that gives protection. It is unclear if the bulwark could fly, or if it ever existed, but stories of the bulwark date back to the Ancient Greeks.
Ah, what a noble history for the mighty bulwark!