I have wondered for years why in Central Illinois where I grew up, we always pronounced yahoo as "yay-hoo". It was a term not necessarily meant as derogatory but meant to designate a man of low reputation, low work ethic, low hygiene care, drunkard, low intelligence, etc. So today in an odd link I clicked on the internet I came up with this story about Daniel Boone. Boone claimed to have killed a creature that matches the description we have today for Bigfoot. Only Boone had no idea what to call it and, according to this article, called it a Yahoo (pronounced today in Kentucky (and Central Illinois) as "yay-hoo", because that sort of matched the cry this creature made. It does make me wonder also if the term "yoo-hoo" had any derivation from this.
Here is the article reference where I found this information. http://www.bfrpky.com/BOONE.html, which was excerpted from the www.appalachianhistory.net .
