The Australian sense almost certainly derives from Gulliver's Travels, despite Holman's report (quote below), since the sound "H" does not occur in aboriginal languages, only in words learnt or adopted from Europeans. (Reference: Bunyips and Bigfoots, Malcolm Smith, Millenium Books, 1996, ISBN 1-86429-081-1.)
yahoo (plural yahoos)
- A rough, coarse, or uncouth person; yokel; lout.
- A loud boisterous person.
- (pejorative) A white person from the former Confederate States of America (i.e., Southern United States).
- (cryptozoology) A humanoid cryptid said to exist in parts of eastern Australia, and also reported in the Bahamas.
- 1835: The natives are greatly terrrified by the sight of a person in a mask calling him "devil" or Yah-hoo, which signifies evil spirit. — James Holman, Travels, 1835 (quoted by Malcolm Smith, above)
- 1985: Yahoos in the Bahamas — title of paper by Michael Raynal, Cryptozoology, volume 4, 1985
- An exclamation of joy.
- A battle cry.