Origin of the Title
The title "Lampoon's Christmas Vacation" reflects the film's connection to the humor magazine National Lampoon. The studio used the Lampoon brand to signal a comedic tone and to link the movie to the magazine's established satirical reputation.
Based on a National Lampoon Story
The movie is adapted from John Hughes' short story "Christmas '59," originally published in National Lampoon magazine. Because the source material came from the Lampoon brand, the studio kept the Lampoon name in the title to highlight that origin.
Branding and Franchise Identity
Adding "Lampoon's" to the title helped position the film within a recognizable comedy franchise. The name signaled a specific style of humor and connected the movie to earlier successful National Lampoon releases.
Summary
In short, the title comes from the National Lampoon magazine brand, the original short story published under that banner, and the studio's decision to use the Lampoon name for marketing and franchise continuity. For more background, see the Lampoon's Christmas Vacation page on IMDb.
