英语词源字典 - 在线词源网站

helpful (adj.)[helpful 词源字典]: late 14c., from help (n.) + -ful. Related: Helpfully; helpfulness.[helpful etymology, helpful origin, 英语词源]
unhelpful (adj.): 1590s, from un- (1) "not" + helpful. Related: Unhelpfully; unhelpfulness.