The making of slang is . . . a sort of living process of language like the scum on wine. Without it there is no wine, no life, no fermentation. Later on, the scum passes as dust and dregs and leaves behind the rich fluid of the wine. A language that has ceased to throw off slang has ceased to live. Thus came all our language. Every syllable of it since the dawn of speech has been rolled over and over in endless renewal. Our oldest words, our oldest names, were once bright with the colours of the morning, striking some new metaphor that brought into full relief the image of the thing seen.
-- Stephen Leacock, How to Write 121 (1943)