It/its

That sentence sits at the end of a long article about grammar. What can be dated is the morphology. What people have meant by applying the pronoun to a person is mostly not in the sources at all.

How its and itself cover the cases

Wikipedia counts three shapes for five word forms. It is both the nominative and the accusative, its is both the dependent and the independent genitive, and itself is the reflexive and the intensive at once.

The article's examples put each in place: It's there as subject, I saw it as object, I touched its top as determiner, It did it itself as adjunct, and the modifier use in They were the it crowd. The reflexive doubles as an intensive, which is the difference between a thing acting on itself and a thing acting alone.

Where it came from in Old English

Old English had one third-person pronoun with three genders in the singular, and its neuter nominative and accusative was hit. The modern word is that form with the h worn off, a change Wikipedia dates to the twelfth century.

The rest of the paradigm took much longer. By the fifteenth century the forms were (h)it in the nominative and the accusative, sometimes him in the accusative, his in the genitive, and (h)it self in the reflexive, spelled a dozen ways. Hit survived well into the sixteenth century and had left formal written English before the seventeenth. The genitive its appeared only in the later sixteenth century and had taken over by the middle of the seventeenth, at which point the word reached its present shape. Both older forms are still spoken: hit persists in some dialects in stressed positions, and some dialects use it rather than its as a possessive.

The gender system moved underneath it. By the seventeenth century the marking of gender on common nouns and adjectives had gone, leaving it on pronouns alone, while a new system of relative pronouns divided personal who from impersonal which. Wikipedia therefore files it under an impersonal gender as well as a neuter one.

Why it was once used of people

In Old English the pronoun for a person could be it as a matter of grammar. Cild, the ancestor of child, was neuter, and so were wæpnedcild and wifcild, male child and female child. Wif, meaning female, was neuter. Mann was grammatically masculine but meant a person, and wifmann, the ancestor of Woman, was grammatically masculine too, because its last element was. The same principle put landwaru, heofonwaru, and helwaru, the inhabitants of a region, of heaven, and of hell, into the feminine, because waru was feminine. Ælfric's Latin vocabulary supplies three Anglo-Saxon words for an intersex person, scritta, wæpnedwifestre, and bæddel, and their endings alone decide their genders. Wikipedia notes that some speakers still use it with child in the present century, and sets the whole arrangement in a wider frame: about half of the world's languages mark gender, along a continuum running from systems keyed to the shape of the word to systems keyed to its meaning. Old English was moving from the first towards the second, and the move was mostly completed in Middle English.

Mark Twain used the effect as a joke. His Tale of the Fishwife and its Sad Fate, in The Awful German Language of 1880, renders German grammatical gender literally into English, so that the rain and the hail and the snow are all he and the fishwife stuck in the mire is it throughout, dropping its basket and cutting its hands. Lewis Carroll had done the same thing straight in Alice's Adventures in Wonderland in 1865, where Alice looks anxiously into the baby's face to see what is the matter with it, and Neil Gaiman did it again in The Graveyard Book in 2008, where a child opens its eyes and stares around it.

No source traced for this entry treats the pronoun as a term of abuse, or dates that use. The record on file carries the grammatical use and the literary one and stops there, which means the entry can describe how it came to be applicable to a person and cannot say when applying it to one became an insult.

What Coleridge proposed for the word person

Samuel Taylor Coleridge wanted the pronoun used far more widely, and for a reason that is recognisable now. He asked, in a note Wikipedia reproduces, whether a neutral pronoun ought not to be used for the word person wherever it carries the sense of a human being of no particular sex, in order to avoid particularising man or woman, or to express either indifferently. Without it, he wrote, the whole use of the word person is lost in a number of instances, or kept only by some stiff and strange arrangement of the words. His conclusion was that the etymology of person authorises it and which in place of he, she, him, her, who, and whom.

At least one writer did it consistently. E. Nesbit wrote of mixed groups of children in exactly that way, including a line about everyone getting its legs kicked or its feet trodden on in the scramble to get out of the carriage. Wikipedia adds one further institutional user, noting that the same usage, set in capitals as though it were an acronym, occurs in District of Columbia police reports.

Who uses it as a pronoun today

Wikipedia's article gives the current fact one line, that some people use it as a gender-neutral pronoun, and supports it with a reference to the 2021 Gender Census, a self-selected community survey.

That is the whole of what the folder behind this entry holds on the subject. There is no figure, no dated first use in this sense, and no account by a person who states the set. A reader looking for the reasoning will not find it in the sources listed below, and this half of the word's record has not been documented to the standard the rest of the entry meets.

Why the dummy it has no referent

A large share of the pronoun's work in English is done with no referent at all. It's raining and it's clear that the answer is wrong both need a subject for syntactic reasons only, and it supplies one.

Wikipedia traces the pattern to a change in the language as a whole. Old English did not require a subject in the way modern English does, and as the requirement developed, verbs that take no arguments needed something to fill the slot. Weather verbs are the obvious group, and the article quotes an Old English line about thunder on Saturday portending the deaths of judges and sheriffs, where the modern translation has to insert an it that the original does not have. Verbs of happening, of seeming, of sufficiency, and of mental states behaved the same way, and one of them is fossilised in the phrase suffice it to say.

The same empty subject turns up in cleft sentences, where a construction such as it's obvious that the answer is wrong uses the pronoun to hold a position that the clause behind it fills.

Whether a given it is a dummy is not always decidable. The article's own example is the exchange asking who is at the door and answering that it is me, where the pronoun has a referent and a syntactic slot at once. Even the dependents behave oddly: the article notes that a relative clause can modify the word, as in a sentence about that not being the it that was meant, which is a construction they and she do not readily take.