Ain’t is possibly the most-maligned word in the English grammar guides. Even though many other contractions are now acceptable in all but the most formal writing, ain’t is still frowned upon in all but the most informal writing, and sometimes even there. But that hasn’t stopped it. Not only has ain’t not disappeared; it has even expanded its reach in recent years.
Let’s start at the beginning: Ain’t has been part of English for about 400 years. It was originally a contraction for am not and are not and was written an’t and a’n’t.
In their book Origins of the Specious: Myths and Misconceptions of the English Language, Patricia T. O’Conner and Stewart Kellerman, summarize ain’t’s history, and speculate on how it fell from grace:
By the early 1700s, it was also being used as a contraction for is not. And by the 1800s it was used for have not and has not, too, replacing an earlier contraction, ha’n’t. As ain’t took on more meanings, it drifted farther and farther from its roots. Contractions like can’t and don’t had clearly traceable parentage, but ain’t claimed to have so many parents that it seemed illegitimate. No wonder language authorities turned up their noses. Since the late nineteenth century, they’ve considered ain’t a crime against good English. (1)
In fact, another source even argues that the modern contractions haven’t and hasn’t were created anew to replace the ha’n’t contraction that turned into ain’t and became unacceptable. (2)
The stigmatization of ain’t is a pity, because without ain’t, there’s a gap in our system of contractions. When you negate the present tense of be and your subject is a pronoun, you usually have a choice between contracting the pronoun and the verb or the verb and the negative word. For example, you can write we’re not or we aren’t, they’re not or they aren’t, and you’re not or you aren’t. The lone exception is I, where your only choice in standard English is I’m not.
In the late 1800s, even as critics of ain’t were beginning to speak up, ain’t began to move beyond the verbs be and have and into the territory of the third major auxiliary verb in English: do. Listen to this example from 1881, which I found in the Corpus of Historical American English, from Joel Chandler Harris’s first collection of Uncle Remus stories: “Brer Rabbit look all roun', he did, but he ain't see no dinner.”
In standard English, the phrase ain’t see would be did not see or didn’t see. Of course, if you’re familiar with Brer Rabbit and Uncle Remus, you know that these stories were adapted from stories told by slaves, and that the English in them is a variety of African American English. The use of ain’t in place of didn’t has by and large been limited to African American English, (3) and even there, according to a 1994 study, (4) it’s much less common than using ain’t for negative forms of be and have.