Aristotle's explanation of how a metaphor works conceives of metaphor not only as comparison between two elements but creation of a third, new meaning: "We all naturally find it agreeable to get hold of new ideas easily: words express ideas, and therefore those words are the most agreeable that enable us to get hold of new ideas. Now strange words simply puzzle us; ordinary words convey only what we know already; it is from metaphor that we can best get hold of something fresh" (Rhetoric, III, 1410b).
A Handlist of Rhetorical Terms, Second Edition, Richard A. Lanham, 1991