From The King's English, by Henry Watson Fowler and Francis George Fowler:

SLANG

An informal nonstandard vocabulary composed typically of coinages, arbitrarily changed words, and extravagant, forced, or facetious figures of speech (Merriam-Webster Dictionary)

With this advice—never to use slang except in dialogue, and there as little as may be—

we might leave the subject, except that the suggestion seems to require justifying. To justify it, we must attempt some analysis, however slight, of different sorts of slang.

To the ordinary person, slang comes from every direction, from above, from below, and from all sides, as well as from the center. What comes from some directions you will know for slang, what comes from others you may not.

You may be expected to recognize words from below. Some of these are shortenings of words whose full form conveys no clear meaning, and is therefore useless, to them. An antiquated example is mob, for mobile vulgus. That was once slang, and is now good English. A modern one is bike, which, of course, is considered good English today.

Though these shortenings are the most easily detected, they are also the best slang; when the time comes, they take their place in the language as words that will last, and not, like many of the more highly descended words, die away uselessly after a brief popularity.

Another set of words that may be said to come from below, since it owes its existence to the vast number of people who are too lazy to appreciate fine shades of meaning, is exemplified by nice and awful. The abuse of nice has gone on at any rate for over two centuries; the curious reader may find an interesting page upon it in the fourteenth chapter of Northanger Abbey (1803). Nice has been adopted by the masses for a mere intensive, in the sense of remarkable.

So much for the slang from below; the ordinary man can detect it. He is not so infallible about what comes to him from above. We are by no means sure that we shall be correct in our particular attribution of the half-dozen words now to be mentioned; but it is safe to say that they all at one time enjoyed some vogue as slang, and that they all come from regions that to most of us are overhead:

Phenomenal came to us from Metaphysics; immanence from Comparative Theology; epoch-making perhaps from the Philosophic Historian; true inwardness from Literary Criticism; cad (which is, it appears, Etonian for cadet) from the Upper Classes; psychological moment from Science; cryptic from Academic Circles; philistine from the region of culture.

Among these the one that will be most generally allowed to be slang—cad—is in fact the least so; it has by this time, like mob, passed its probation and taken its place as an orthodox word, so that all who do not find adequate expression for their feelings in the orthodox have turned away to bounder.

By the slang that comes from different sides or from the centre we mean especially the many words taken originally from particular professions, pursuits, or games, but extended beyond them. Among these a man is naturally less critical of what comes from his own daily concerns, that is, in his view, from the centre.

Frontispiece, for face, perhaps originated in the desire of prize-ring reporters to vary the words in their descriptive flights. Negotiate (a difficulty, etc.) possibly comes from the hunting-field; people whose conversation runs much upon a limited subject feel the need of new phrases for the too familiar things.

We now add a short list; some of the words and phrases on it were once slang and have passed into acceptable idiomatic use. Others were once slang and have since passed out of use. Most of them can be referred with more or less of certainty to particular occupations. Whether they were originally recognized as slang certainly depended in part on whether the occupation was familiar, though sometimes the familiarity will disguise, and sometimes it will conceal the slanginess.

To hedge, the double event (turf); frontal attack (war); play the game, stumped (cricket); to run—the show, etc.—(engine-driving); knock out, take it lying down (prize-ring); log-rolling, slating, birrelling (literature); to tackle—a problem, etc.— (football); to take a back seat (coaching?); bedrock, to exploit, how it pans out (mining); whole-hogging, world policy (politics); floored (1. prize ring; 2. school); the under dog (dog-fighting); up to date (advertising); record—time, etc.—(athletics); euchred, going one better, going Nap (cards); to corner—a thing— (commerce)—a person—(ratting); chic (society journalism); on your own, of sorts, climb down, globetrotter, to laze (perhaps not assignable).