The words “happy” and “hour” have appeared together for centuries when describing pleasant times. In act I, scene 2 of William Shakespeare’s King Henry V (said to have been written in about 1599), for example, King Henry says, “Therefore, my lords, omit no happy hour That may give furtherance to our expedition . . . .” The use of the phrase, “Happy Hour,” to refer to a scheduled period of entertainment, however, is of much more recent vintage.
One possible origin of the term “Happy Hour,” in the sense of a scheduled period of entertainment, is from the United States Navy. In early 1913, a group of “home makers” called the “Happy Hour Social” organized “semi-weekly smokers” on board USS Arkansas. The name “Happy Hour Club,” “Happy Hour Social Club,” and similar variants, had been in use as the names of social clubs, primarily by women’s social clubs, since at least the early 1880’s. By June 1913, the crew of Arkansas had started referring to their regularly scheduled smokers as “Happy Hours.” The “Happy Hours” included a variety of entertainment, including boxing and wrestling matches, music, dancing and movies. By the end of World War I, the practice of holding “Happy Hours” had spread throughout the entire Navy.
The Random House Dictionary of American Slang dates “Happy hour,” as a term for afternoon drinks in a bar, to a Saturday Evening Post article on military life in 1959. That article detailed the lives of government contractors and military personnel who worked at missile-tracking facilities in the Caribbean and the Atlantic. “Except for those who spend too much during ‘happy hour’ at the bar – and there are few of these – the money mounts up fast.” Barry Popick’s online etymology dictionary, The Big Apple, lists several pre-1959 citations to “Happy Hour” in print, mostly from places near Naval bases in California, from as early 1951. – wikipedia