If you’ve ever wondered where the term comes from:
The term “happy hour” originated from sailors in the United States Navy who used the term to describe the period of time during the day scheduled for entertainment. In the 1920′s, sailors would use this time to relieve the stresses of life on the ship by consuming a few drinks and watching boxing or wrestling matches. They referred to the word “happy” as the feeling they got during this free time and the state of mind they entered after a few drinks.
One possible origin of the term 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 the U.S.S. Arkansas (BB 33). By June 1913, the crew referred to the 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.
While this U.S. Navy stuff is the real origins, the term entered pop culture (purportedly) in a 1959 Saturday Evening Post article.