I can't stand the stuff myself*, but linguistically 'macaroni' as a word is interesting.
Obviously it comes from Italian, originally as 'maccaroni' and later 'maccheroni' and, as already pointed out orginally just meant pasta.
The first recorded usage in English is from Ben Jonson, a contemporary and fellow playwright of Shakespeare's. It was then defined as 'a kind of wheaten paste, of Italian origin, formed into long tubes and dried for use as food'.
QuoteHe doth learne‥to eat ænchouies, maccaroni, bouoli, fagioli, and cauiare.
The first mention in English of macaroni with cheese is from 1769 in a Mrs. Raffald's book The Englishe Housekeeper where she writes of dressing macaroni with parmesan.
Quote[1769 E. Raffald Experienced Eng. Housekeeper xii. 261 To dress Macaroni with Permasent Cheese.‥ Boil it‥, pour it on a Plate, lay all over it Permasent Cheese toasted.]
The usage of the word arose about 1760 and referred to young men who had travelled and affected the tastes and fashions prevalent in continental society. So a dandy. This usage seems to be from the name of the Macaroni Club, a designation probably adopted to indicate the preference of the members for foreign cookery, macaroni being at that time little eaten in England.
The name also refers a type of penguin, Eudyptes chrysolophus or a macaroni penguin.
It is also a type of poem in which two or more languages are mingled together, a type of walking stick, a woodworking knife/chisel and in Australian slang 'nonsense'or 'meaningless talk'.
As to Mac and Cheese, it was never called that in the UK until recently when the Americanism crept in. It was always 'macaroni and cheese' or, more often, 'macaroni cheese'.
There is credible evidence that it was first introduced to the Americas by Scottish emigrants to Canada and then travelled south. The Scots got it from Italian immigrants to Scotland.
* My mother made it often and it was the only food I refused to eat no matter how many threats of severe punishment! The rest of the family loved it. One of my brothers so much so that for years my mother had to ship packs of Marshall's Macaroni to him in Spain where he lives and has three restaurants. He won't eat any other brand.
Beats me.
As you can see, it is 'elbow pasta' but never called that in the UK. It's just macaroni.