"I ain't got no money" [duplicate]

I know the ultimate meaning of this is "I have no money."

But why? If ain't means have not, then isn't it true that "I ain't got no money" would be read as "I have not got no money"?

Can I have not got [no money] be interpreted as double negative, and hence determining that "I have money", which is not the true meaning of such saying?

Solution 1:

Ain't, in I ain't got no money means have not. With that meaning, it originally represented the London dialect, which uses sentences such as they ain't got nothing to say.

About the usage of ain't, the NOAD has the following notes:

The use of ain't was widespread in the 18th century and is still perfectly normal in many dialects and informal contexts in both North America and Britain. Today, however, it does not form part of standard English and should not be used in formal contexts.

The sentence then contains a double negative, but the double negative is sometimes used to give emphasis to a negative.
The NOAD has the following notes, about the usage of double negatives:

According to standard English grammar, a double negative used to express a single negative, such as I don't know nothing (rather than I don't know anything), is incorrect. The rules dictate that the two negative elements cancel each other out to give an affirmative statement, so that, logically, I don't know nothing means I know something. In practice, this sort of double negative is widespread in dialect and nonstandard usage and rarely causes confusion about the intended meaning. Double negatives are standard in other languages such as Spanish[, Italian] and Polish, and they have not always been unacceptable in English. They were normal in Old English and Middle English and did not come to be frowned upon until some time after the 16th century. The double negative can be used in speech or in written dialogue for emphasis or other rhetorical effects. Such constructions as has not gone unnoticed or not wholly unpersuasive may be useful for making a point through understatement, but the double negative should be used judiciously because it may cause confusion or annoy the reader.

Solution 2:

Multiple negation has been a feature of English for centuries and is found in the work of at least two of the language’s most revered writers. Once again, we must blame the eighteenth century grammarians for proscribing this most natural of English constructions. Such has been their influence that Standard English no longer allows multiple negation, although other dialects do.

The justification for the prohibition given above is now the usual one. It is demolished thoroughly by Jenny Cheshire (Professor of Linguistics, University of London) in that excellent book edited by Laurie Bauer and Peter Trudgill, ‘Language Myths’. As ‘The Cambridge Guide to English Usage’ tells us:

The appeal to mathematics and logic is irrelevant when languages clearly do use double negatives (they are standard in languages such as French and Russian). No one hearing the song line I can’t get no satisfaction would doubt that it was meant to be an emphatic negative, with the second negative word reinforcing the first.

Solution 3:

That's the whole idea of using the double negative here -- to emphasize the fact you have no money at all. Beware this is very informal and should be used only when you know why you're using it.

Solution 4:

In some English dialects, the proper way to negate a sentence is to negate every negatabile portion of it. This is called Negative Concord. Supposedly French and Spanish work this way too.

There are also some dialects where it is acceptible to subsitute ain't for don't. In a dialect with both properties(eg: AAVE), the negative of "I have some money" would typically be "I ain't got no money".

However, the dominant AmE dialect (SAE) does not have these features, and the dialects (at least in the USA) that do tend to be ones spoken in the South or by poorer African Americans. Thus using this phrase is an instant tip-off (to an American) that they are speaking to someone heavily influenced by one of these communities (steriotypically someone poor and/or uneducated in "proper" AmE).