Here's an excerpt from a webpage on the history of meat hats:
The expression “I’ll eat my hat” traces back as far as the 19th century, usually credited to Abraham Lincoln in reference to one of his trademark stovepipe hats, which were often made of tenderloin...The popularity of meat hats began to fade in the twentieth century, especially during the depression of the 1930’s. Indeed, few people had the luxury of wearing meat on their heads, needing instead to feed their families with it.The hightened disgust is not simply the idea of matter being out of place; afterall, chocolate and vegetable clothing doesn't disgust us. So why is meat more disgusting to wear than leather?
Does meat make the death and fleshines of the animal more visible and disturbing? Or does it have to do with meat supposed to being "inside" (covered by skin or consumed) while leather is supposed to be adorned on the "outside" (hence the revulsion some people have toward eating leather)? Or is there an evolutionary reason: we're grossed out because spolied meat carries disease?