@matigo The story behind the name is that, when receiving their daily ration of alcohol, sailors would pour a bit onto some gunpowder and try to light it. If it didn't light up, they'd know someone had diluted their ration.
I think it takes 100 proof (50% ABV) to light up. Generally "navy strength" bottlings are 50–60% ABV; tonight's is Four Pillars, which I think is 54%.