I think you misunderstand. The way Wikipedia uses the word is the original usage, so only funny if you don’t know about it. Applying it to bar fights and such is the tongue-in-cheek usage.
From Latin belligerans (“waging war”), present active participle of belligerō (“I wage war”), from belliger (“waging war, warlike”), from bellum (“war”) + -ger (from gerō (“I lead, wage, carry on”)).