The word "万不得已" is formed by combining four characters: 万, meaning "ten thousand" or figuratively "extreme"; 不, meaning "not"; 得, meaning "to have to" or "to obtain"; and 已, meaning "to stop" or "to cease". These characters are arranged sequentially to convey the literal sense of "extremely not have to cease", which semantically develops into the idea of being compelled to act only when all other options are exhausted, thus idiomatically meaning "as a last resort".