The question has bothered me for decades. We sang “Yankee Doodle” plenty of times at school, but nobody seemed to wonder why he would say that “a feather in his cap” was “macaroni.”
At last, I found the answer, in Thomas Wright’s book “Caricature History of the Georges” (1860), which examines political and social satire drawings during the reigns of England’s King Georges I, II, and III. A very interesting book, if you’re interested in English history. Despite what the title might suggest, most of the book is text, not pictures. The author notes that for a while in the late 18th century, magazines often did 3-word book reviews. So let’s call this book “clever, erudite, tory.”
On pages 258-61, we learn that during the reign of George II, “men of fashion” were called “beaux.” In 1749, “fribble” became the new term, and this persisted into the reign of George III. In 1772, things changed. Rich young men who had made the tour of the continent came back with new fashions of all kinds; thanks to the wealth pouring in from India, the time was one of extravagant frivolity. The young men formed a club which soon took the name of the unusual Italian dish which it served. For the gentlemen of the Macaroni Club, “it was their pride to carry to the utmost excess every description of dissipation, effeminacy of manners, and modish novelty of dress.” The Macaronis of 1772 “were distinguished especially by an immense knot of artificial hair behind, by a very small cocked-hat, by an enormous walking stick, with long tassels, and by jacket, waistcoat, and breeches, of every close cut.”
Then in 1773 the Macaroni fashion changed to “the elevation of the hair, and the adoption of immense nosegays in the bosom.”
So the mystery of Yankee Doodle is solved. He is an American rube and rustic. He naively thinks that a mere feather in his cap makes him an ultra-fashionable “macaroni.”
It turns out that I could have learned the truth by just looking up “Yankee Doodle” and “Macaroni” in Wikipedia. But at least I finally understand.