bitterness (n.)youdaoicibaDictYouDict[bitterness 词源字典]
Old English biternys "bitterness, grief;" see bitter + -ness. Figurative sense (of feelings, etc.) is attested earlier than literal sense (of taste), which will surprise no one who reads any amount of Anglo-Saxon literature. [bitterness etymology, bitterness origin, 英语词源]