Similar to yours: family friends when I was growing up had a dog named "Dammit" because when they got the dog as a puppy, it would misbehave, and they kept saying things like "Dammit get outside!", "Dammit what did you do to the pillow?", etc. It's worth pointing out that these people were incredibly nice, just a little salty.
Eventually the dog just responded like Dammit was its name, so it stuck.