A character in D.H. Lawrence's novel Women in Love (published 1920) calls out, "Shu-hu!" to hail her sister in a crowded place.
This must be the same as "yoo hoo". What is the source of this exclamation?
The Oxford English Dictionary dates yoo-hoo to 1924, as noted by the American Dialect Society, and compares it to yo-ho, originally a nautical phrase also sometimes used in yo-heave-ho.
Their first documented use of yo-ho is from 1769 in William Falconer's An universal dictionary of the marine:
Yo-ho derives from two interjections. Yo: an exclamation of incitement or a warning, first documented around 1420. And ho: "an exclamation expressing, according to intonation, surprise, admiration, exultation (often ironical), triumph, taunting" from before 1400, and also "a sailor's cry in heaving or hauling".
It's doubtful there is a single documented "source". If it was already part of American vernacular, it may have shown up in several publications almost simultaneously. Pinpointing the first use in print does not really tell us the "source" because the publication did not coin the exclamation.
The American Dialect Society's Dialect Notes, Volume 5 in 1927 records that it is used to call attention (p280). In 1919, William La Vare's Up the Mazaruni for Diamonds uses it for that purpose. The earliest I could find was from c. 1916 in The Vassar miscellany monthly.
The obscurity of these texts appears to indicate that there was no publication responsible for disseminating the exclamation's use. Someone used the expression at some point (perhaps a variation of "yo-ho" or "you-who" or any other of the myriad plausible, but unsubstantiated, explanations) and it caught on.