USE OF DOUBLE NEGATIVES.
The old usage.
453. In Old and Middle English, two negatives strengthened a negative idea; for example,—
He nevere yet no vileineye ne sayde,
In al his lyf unto no maner wight.
—Chaucer.
No sonne, were he never so old of yeares, might not marry. —Ascham.
The first of these is equivalent to "He didn't never say no villainy in all his life to no manner of man,"—four negatives.
This idiom was common in the older stages of the language, and is still kept in vulgar English; as,—
I tell you she ain' been nowhar ef she don' know we all. —Page, in Ole Virginia.
There weren't no pies to equal hers.—Mrs. Stowe.
Exceptional use.
There are sometimes found two negatives in modern English with a negative effect, when one of the negatives is a connective. This, however, is not common.
I never did see him again, nor never shall.—De Quincey.
However, I did not act so hastily, neither.—Defoe.
The prosperity of no empire, nor the grandeur of no king, can so agreeably affect, etc.—Burke.
Regular law of negative in modern English.
But, under the influence of Latin syntax, the usual way of regarding the question now is, that two negatives are equivalent to an affirmative, denying each other.
Therefore, if two negatives are found together, it is a sign of ignorance or carelessness, or else a purpose to make an affirmative effect. In the latter case, one of the negatives is often a prefix; as infrequent, uncommon.