Youse

Youse (pronounced yooz, yuhz or yiz (in ascending order of boganess))

A non-standard pronoun; an alternative form of “you” (usually when addressing or referring to two or more people).

1876: A dialectal inflection of you, first noted as being used in plural senses but also as a simple alternative to you; sometimes spelled yous, mostly in the US.  Some sources cite 1893 as the first known citation but most reference 1876 and the other forms, y'all & you-uns, are US variations, found mostly south of the Mason-Dixon Line.  Although undocumented, use likely dates from the early days of English.  Urban Dictionary notes the existence of "you'se", apparently an alternative to "you're" (their example of use was "You'se a bitch!" so it may be handy in the right company).  

As a plural, it’s most prevalent in (Northern) England, Scotland, Ireland, Australia, New Zealand, South Africa, northern Nova Scotia, parts of Ontario, the north-eastern United States (especially areas like Boston with high rates of Irish immigration) and in Mexican-American communities in the southwest.  It’s also widely used in Scouse.  As a singular, it’s most common in Philadelphia, New York, Boston and in working class Italian-American communities.  Like most of the English-speaking world, in Australia, youse is a class-identifier and thought exclusively bogan, which, for those for whom English isn’t a first language, is a little unfair because (1) it would be a useful word if acceptable and (2) for later adopters of English it must seem strange youse is wrong because, as a plural formation, technically, it follows the rules.

Descriptive vs Prescriptive Dictionaries

Structural linguistics can be either descriptive or prescriptive, the former documenting how words are used by the folk using them, the latter a codification of the rules (spelling, pronunciation, grammar etc) which define how language should be used.  Samuel Johnson's (1709-1784) A Dictionary of the English Language (1755) wasn’t the first dictionary but was one of the most influential and it’s a hybrid, full of amusing and idiosyncratic entries as well as many errors but it all reflected the author’s understanding of the language as it existed; what was right and wrong as well as what was actually done.

In the US, "youse" is a regionalism and the New York Times claimed that when referring to groups of two or more, other forms were anyway more popular in different parts of the country.  It does however seem to appear disproportionately in US film & television, presumably because it works well as an ethnic & class identifier.  On the "Streets of America" in Disney's Hollywood Studios, there are many façades but one structure which is real is Youse Guys Moychindice, a souvenir kiosk in the style of those still seen in films set in New York City and stereotypically run by Italian & Irish-Americans.  Youse Guys Moychindice stocks a variety of snacks, hats, cups, plush toys and assorted gifts.

As the rules of English became increasingly standardised, dictionaries tended to being prescriptive (OED, Cambridge, Webster’s et al) texts which were lists of correct words and their meanings, lexicons of that which conformed to accepted rules.  Then, later, there were dictionaries of slang which documented English as it was actually spoken with its inventions, malapropisms, the often inexplicable and the frequently ephemeral; these were the descriptive works.  As dictionaries either moved or replicated their print editions online, the distinctions were maintained and refined.  Merriam-Webster for example publishes print editions which include only formal, correct English whereas the dynamic online version is inclusive or promiscuous, depending on one’s view.

English anyway has no centralised authority which defines right and wrong as the Académie française and Goethe-Institut respectively provide for French and German, the evolution of English being organic.  So, if a word like youse is either to endure as a bogan niche or gain the critical mass of middle-class acceptance will depend entirely on users of the language and eventually, dictionaries will reflect this.  Use and meanings in English do change; there are words now contronyms, things which in modern use, now mean the opposite of their classical origins.