Sometimes it makes sense, but there's a weird/brutal humor to it, as well. And none more than in the cases of St. Denis and St. Apollonia.
St. Denis, a 3rd century Roman, was the first bishop of Paris, responsible for many conversions. As part of Emperor Decius' persecution of Christians, Denis was imprisoned, tortured and beheaded.
But then, in a move that is itself Python-ready, his headless body picked up his head and carried it 10 kilometers, the head itself preaching the Gospel the whole time.
Now, what would you make such a man patron saint of? Paris? The unjustly condemned?
How about--and I swear I'm not making this up--headaches?
That's right. Saint Denis, whose head was literally severed from his body, is the patron saint of headaches.
And if you like that, how about this: as an elderly woman Saint Apollonia found herself in a nasty anti-Christian mob. The pack smashes out all her teeth, poor thing, and then dragged her to a fire, where they threatened to burn her to death if she didn't renounce her faith. Rather than do so, she flung herself into the flames and died.
You might think Apollonia is the patron saint of fire safety. Close. She's the patron saint of dentists and those needing dental care. And if fact she is often presented, as below, wearing a necklace made of her own teeth:
Or, even better, like so:
I swear she's a dead ringer for my dental hygienist.
It's a weird world.