deadwood (n.)youdaoicibaDictYouDict[deadwood 词源字典]
1887 in figurative sense of "useless person or thing," originally American English, from dead (adj.) + wood (n.). Dead wood in a forest is useful as firewood; perhaps the reference here is to the dried up parts of plants grown for commercial production of flowers or fruit.[deadwood etymology, deadwood origin, 英语词源]