The weapon got its name from this passage from a newspaper printed during the Occupation of Milithian.
Milithian has a faithful cannon parked in the heart of a lake, and when she fires, she seldom fails to send the shot home.
- Urnst, excerpt from the Milithian Gazetter, "The Living Dead Assail Milithian"
During the Occupation of Milithian, the garrison used this great weapon to inflict serious damage on the Ghul Armada, and sunk the flagship of Jairall Bloodtusk. To prevent its capture, the Milithian Navy scuttled the mammoth barge holding Ole' Faithful. Years later, it was raised from the harbor and moved inland to serve as a monument to the bravery of the garrison.
The weapon has since been copied and is manufactured by the more advanced civilizations of the realms.