The history of the English language has been one of perpetual expansion, its richness and diversity in usage its greatest resource. Coinage and invention, adaptation, amalgamation and transmutation of words and their sources have kept our language dynamic, in a constant state of organic growth and change. This has given rise to the linguists' discourse of plural 'Englishes', used to describe a language which is emphatically not monolithic but has spawned a myriad variants of different kinds, be they pigeons and creoles, regional and local dialects, or the argots of any other community or practice, from rap to text messaging. Against this background of perpetual innovation, dictionaries will always struggle to keep up, and to do justice to that plurality.
In case we take our linguistic diversity and pluralism for granted, it's worth reflecting on the contrast with the French language, notoriously subject to the literary and cultural policing of the Academie francaise. This august institution, formally established in 1635, acts as a regulatory body, attempting to outlaw encroachments from other languages and stem the tide of hybridisation threatening the purity of the French tongue with the inventions of Franglais and the like. In seventeenth-century France, the highest literary values were placed on linguistic refinement and restraint: the vocabulary of Racine is a fraction of the size of Shakespeare's, and offers a telling contrast with our own tradition of linguistic promiscuity and freedom of invention. Such a fate might perhaps have been our own (though it's hard to imagine), since the eighteenth century saw a vigorous public debate on whether an Academy should be established in Britain, to provide an authority that would pronounce on correct usage and promote aspirations towards order and fixity, for a language whose evident instability in the hands of its users had become a source of profound cultural anxiety.
Debating 'dyversitie and chaunge'
The roots of this question go back into the sixteenth century, when the translation of classical and continental texts was provoking a sense of the English language's inadequacy to meet the demands of Renaissance thought. A debate ensued over whether enriching resources should be sought in the classical and European languages, or in the revival of native vocabulary and derivations. The introduction of printing heightened the sense of the English language's instability--its general lack of system or rule (before the first dictionaries were produced), and the proliferation of word forms, meanings, pronunciations and spellings--by contrast with the fixity of dead languages like the classics. Caxton himself had highlighted the issue of 'dyuersitie and chaunge of language' in his prologue to a translation of Virgil in 1490, not least in relation to the compositor's dilemma 'bytwene playn, rude and curyous' variants, observing in the earliest stages a tension which still persists between oral freedom and the desire for standardisation in the printed record.
It soon became apparent that such tensions were not simply a linguistic matter. Wilson's Arte of Rhetorique in 1553 set out a straight choice between adopting established social distinctions which separated 'courte talke' and 'countrey speache' or standardising so as to 'vse altogether one maner of language'. Puttenham's Arte of English Poesie went further in 1589 in advocating a regionally-based standard for literary language, excluding the rich linguistic resources of half the country in the process:
neither shall he take the termes of Northern-men, such as they vse in dayly talke ... nor in effect any speach vsed beyond the riuer of Trent, though no man can deny but theirs is the purer English Saxon at this day, yet it is not so Courtly nor so currant as our Southerne English is; no more is the far Westerne mans speach. Ye shall therefore take the vsuall …