impossible

Impossible means that something cannot be done or happen. Its history is recorded in Middle English, where it was formed from im- plus possible. The negative prefix im- comes through Latin: it is an assimilated form of in-, used before b, p, or m, and ultimately traces through Proto-Italic forms to Proto-Indo-European né and n̥-.

The other part, possible, came into Middle English from Old French possible, from Latin possibilis, meaning “possible,” related to posse, “to be able.” The word appears in Shakespeare’s The Tempest, written in 1610–1611, in Antonio’s question, “What impossible matter will he make easy next?” It later broadened beyond literal impossibility: by 1787 it described something that could not be the case, and in colloquial use it can describe a person or situation that is extremely difficult to deal with. It is also recorded as a noun meaning an impossibility.