Originally 'Yippee' based on Bruce Willis' famous Die Hard line, changed due to copyright
Short for "You Always Have Other Options" as a statement of competition with rival engines
It's the first word the founders searched to test their engine
Short for "Yet Another Hierarchical Officious Oracle"
 
Correct Answer: Short for "Yet Another Hierarchical Officious Oracle"

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Created in January 1994 at Stanford University by electrical engineering graduate students Jerry Lang and David Filo, Yahoo was originally called "Jerry and David's Guide to the World Wide Web," which was a directory of other sites organized in a hierarchy. By January 1995, the pair had created the domain name yahoo.com and thus the service was renamed to "Yahoo!".

Although the creators have said they selected the name Yahoo because they liked the word's reference to an uncouth, ignorant person (a slang definition derived from the primitive Yahoos of Jonathan Swift's 1726 novel Gulliver's Travels), it was later decided by Lang and Filo that "Yet Another Hierarchically Organized Oracle" or "Yet Another Hierarchical Officious Oracle" was a suitable backronym for the name Yahoo (backronym being an acronym intentionally formed around a word or phrase).