In January 1994, Jerry Yang and David Filo were electrical engineering graduate students at Stanford University when they created a website named "Jerry and Dave's Guide to the World Wide Web", a directory of other websites, organized in a hierarchy, as opposed to a searchable index of pages.
In March 1994, "David and Jerry's Guide to the World Wide Web" was renamed "Yahoo!".
The word "yahoo" is an acronym for "Yet Another Hierarchical Officious Oracle". The term "hierarchical" described how the Yahoo! database was arranged in layers of subcategories. The term "oracle" was intended to mean "source of truth and wisdom," and the term "officious," rather than being related to the word's normal meaning, described the many office workers who would use the Yahoo database while surfing from work.
However, Filo and Yang insist they mainly selected the name because they liked the slang definition of a "yahoo" (used by college students in David Filo's native Louisiana in the late 1980s and early 1990s to refer to an unsophisticated, rural Southerner): "rude, unsophisticated, uncouth."
Yahoo! was incorporated on March 1st, 1995.