Thorne - Dictionary of Contemporary Slang 3e

Slang is language deliberately selected for its striking informality and is consciously used in preference to ‘proper’ speech (or, more rarely, writing). It usually originates in small social groups. For these groups, it is a private code that embodies their particular values and behaviour and reinforces their exclusivity. Slang expressions may escape the originating group and become more widely used, and although slang draws much of its effect from its novelty, some terms (booze, punk, cool) may stay in the language for many years....