ballyhoo: boisterous publicity; commotion; noisy, extravagant talk
Ballyhoo was first used as a word for the noisy advertising that went on outside carnival tents, designed to draw in crowds to see the show. The word's origin is obscure. Writing in a 1935 American Speech article, Charles Wolverton describes letters he received from an old carnival man who claimed that it originated at the 1893 Chicago World's Fair. According to this story, one of the exhibits featured a pair of Turkish whirling dervishes. As they spun and jumped, they cried "B'Allah hoo." (Wolverton interprets this as Arabic for "God! He!") When they were fired for failing to draw a crowd, they stood outside the tent and performed for free, attracting a much larger audience than they had inside the tent. Thereafter, when their showman boss wanted them to draw a potentially ticket-buying crowd, he communicated this idea by crying, "Ballyhoo!"
An alternative to this intricate explanation is that the word is a shortened form of Ballyhooly. Ballyhooly is an Irish town famous for more and better street fights than usual. It has occasionally been used to mean commotion or a noisy scolding, as in this example from Tait's Magazine for August, 1837: "By Jasus! he gave him Ballyhooly, the d____d insolent son of a sign-painter!" Some people have suggested that ballyhoo is connected to ballahoo, nineteenth-century nautical slang for an old worn-out vessel. However, there is no evidence to support this derivation.
The 1920s were known as "The Age of Ballyhoo" because sensationalism took a sharp rise after World War I. Aggressive advertising, including promotional campaigns run by ballyhoo artists, also developed in the twenties. It almost goes without saying that ballyhoo can be a verb or an adjective as well as a noun.
Shill is another American slang word related to carnival advertising.