Here's the story behind Duvel ("devil"). I suspect this is usually the story: alcohol associated (teasingly) with evil. There are also lots of copycat names.
To commemorate the end of World War I, the Moortgats named their main beer Victory Ale. But during the 1920s, an avid drinker described the beer as "nen echten duvel" (a real devil in Brabantian Dutch) - perhaps in reference to its formidable alcohol content (8.5% ABV) - and the name of the beer was changed to Duvel.