Gates of horn and ivory

The gates of horn and ivory are a literary image used to distinguish true dreams (corresponding to factual occurrences) from false. The phrase originated in the Greek language, in which the word for "horn" is similar to that for "fulfill" and the word for "ivory" is similar to that for "deceive". On the basis of that play on words, true dreams are spoken of as coming through the gates of horn, false dreams as coming through those of ivory.