Powerless is from power + -less. Power derives from Old French poeir ('to be able'), from Vulgar Latin potere, from Latin posse ('to be able'). Important recorded forms include poeir (Old French) and posse (Latin). Morphologically, the word preserves a built structure whose named elements carry the historical sense into English. The modern sense remains close to that composition, with the parts narrowing into a single lexical item. In current use it covers without the ability, influence, or strength to act or change things. The wider family includes derived forms such as powerlessly and powerlessness and related words such as power and powerful.