...sed in nomine diabli!
It's no mistake that Ahab spoke in Latin when he baptized his Moby Dick-killing harpoon. The white whale that had driven him mad with lust for vengeance (the beast had taken his leg) was itself a kind of demon. At least as far as Ahab was concerned.
It's worthwhile to note that Ahab's false leg was made of whalebone.
Ahab had sacrificed his razors to be the foundation of the fiercest harpoon his smith could forge, forswearing shaving until Moby Dick was dead (preferably by his hand). Melville did not note whether Ahab gave up other hygienic tasks, though it's fascinating to me that he also gave up smoking during the hunt.
Rather than tempering his hot-from-the-forge harpoon in water, as was the custom, he caused the non-Christian crew members to fill a vessel with their blood. His harpoon, the blade of which was struck by lightning as Ahab held it aloft, was founded on his personal effects--thereby imbuing it with his intense hatred--and tempered in the blood of savages before he spake the words that translate:
"I baptize you not in the name of the father, but in the name of the devil!"
He was a bit obsessive.