In a bilious manner; with anger, irritability, or bad temper; marked by or showing bitterness or ill will.
From 'bilious' (angry, irritable, or relating to bile) + '-ly' (adverb suffix), where the original reference to an excess of bile evolved into meaning a bad mood or angry disposition.
Medieval doctors thought personality came from body fluids—too much bile meant you were angry and grumpy (they called it the 'choleric' temperament), which is why 'bilious' still means irritable today!
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