H. L. Mencken

“ In our own time, with thou passed out entirely, even as a pronoun of contempt, the confusion between you in the plural and you in the singular presents plain difficulties to a man of limited linguistic resources. He gets around them by setting up a distinction that is well supported by logic and analogy. “I seen yous” is clearly separated from “I seen you.” And in the conjoint position “yous guys” is separated from “you liar.”
Let us now glance at the demonstrative and relative pronouns. ”

“ So long ago as the fifteenth century the old clear distinction between ye, nominative, and you, objective, disappeared, and today the latter is used in both cases. Sweet says that the phonetic similarity between ye and thee, the objective form of the true second singular, was responsible for this confusion. [10] In modern spoken English, indeed, you in the objective often has a sound far more like that of ye than like that of you, as, for example, in “how do y’ do?” and in American its vowel takes the neutral form of the e in the definite article, and the word becomes a sort of shortened yuh. ”

“ After all, the verb of being is fundamentally transitive, and, in some ways, the most transitive of all verbs, and so it is not illogical to bring its powers over the pronoun into accord with the powers exerted by the others. I incline to think that it is some such subconscious logic, and not the analogy of “it is he,” as Sweet argues, that has brought “it is me” to conversational respectability, even among rather careful speakers of English. ”

“ Both forms represent a doubling of inflections, and hence grammatical debasement. On the side of the yours-form is the standard usage of the past five hundred years, but on the side of the yourn-form there is no little force of analogy and logic, as appears on turning to mine and thine. In Anglo-Saxon, as we have seen, my was min; in the same way thy was thin. During the decadence of the language the final n was dropped in both cases before nouns—that is, in the conjoint form—but it was retained in the absolute form. This usage survives to our own day. ”

“ In the lower reaches of the language the plural seems to get into every sentence of any complexity, even when the preceding noun or pronoun is plainly singular. Such forms as “every man knows their way,” and “nobody oughter never take what ain’t theirn” are quite common.
In demotic American the pedantry which preserves such forms as someone’s else is always disregarded; someone else’s is invariably used. ”

“ Krapp explains this use of who on the ground that there is a “general feeling,” due to the normal word-order in English, that “the word which precedes the verb is the subject word, or at least the subject form.” [9] But this explanation is probably fanciful. Among the plain people no such “general feeling” for case exists. Their only “general feeling” is a prejudice against case inflections in any form whatsoever. They use who in place of whom simply because they can discern no logical difference between the significance of the one and the significance of the other. ”

“ Those-there, if I observe accurately, is still pronounced more distinctly, but it, too, may succumb to composition in time. The adverb will then sink to the estate of a mere inflectional particle, as one has done in the absolutes of the thisn-group. ”