The story
From October + -fest, after German Oktoberfest.
Etymology from Wiktionary, CC BY-SA 4.0.
Today it means: The Bavarian holiday (Oktoberfest or Wiesn), or any such holiday, celebrated in late September to early October, typically featuring German music, cuisine, and beer-drinking as prominent activities. Full definition →
From October + -fest, after German Oktoberfest.
Etymology from Wiktionary, CC BY-SA 4.0.