Usage of "all" in phrases like "how all" and "where all"

Question

I'm an Englishman with friends all over the world, including two from Florida. I've observed both using the word "all" in a manner that appears unique to the area – certainly I've never read of its use online or heard it spoken aloud. The usage is as follows:

Where all have you visited so far?

What all bands are you into?

The addition of the word is quite intentional; it is used to explicitly indicate that the speaker wishes to hear the sum of all possible answers to the question where a word like "other" or "else" would imply a fair selection to be sufficient.

Grammatically I have my doubts about the usage of the word in this context, but it's clearly in use, chiefly (it would appear) in Florida, making the "right/wrong" argument both moot and unnecessary. I would like to know, however, how popular this particular usage is and where (if anywhere) the readers of this question have heard or seen it in use.

Answer 1

The collocation of the interrogatives where, what, and who with all features in the dialect of northeast Scotland, while in West Ulster, the all can float somewhat. Given settlement patterns in the American South, it should hardly be surprising that such forms are still current from Texas to Virginia, including how all, which is unknown in Scotland. Note, for instance, that Scots and Southern American, at least for older speakers, are the only flavors of English where the wine-whine merger has not occurred.

It is, however, in Indian English where interrogative+all is most fully developed, and such constructions are felt as plurals. While an American from the South might ask "Who all was at the party?" an Indian will do so with a plural verb. Indian English has also added when all, which is not used in Scots or Southern American.

Answer 2

The construction was very common among all the southerners I knew from my childhood in East Alabama and college in Tennessee, without regard to education or social or economic status. (I cannot speak to speakers of AAVE, with whom I had very little colloquy: these were the years before integration.)

When-all, where-all, what-all, which-all, why-all and the rest are the plurals of the respective proforms which head them. They don't necessarily demand an exhaustive list, but signal the speaker's expectation of plural answers.

(Compare the 2nd person plural you-all.)

They are not usually employed to introduce bound relative clauses, but are frequently employed throughout the southern US to introduce interrogatives and free relative clauses.