Dastardly

A dastard is a coward, or a pusillanimous individual; although 'dastardly' seems to have taken on a more generic, negative 'bad person' vibe. But what's nice about this synonym for coward (according to the dictionaries) is that 'it is derived most likely from Old Norse dæstr, exhausted'. There's something splendidly psychologically true about the notion that cowardice is not a sort of Falstaffian force of character, and more a function of the myriad forms of exhaustion.