Facts below show LSD was out 12 years before the Bus and was used for trips 7 years before. The beleif it was the mini windows is an old wives tale as the first buses did not have the windows and the term was used prior to that optin

The psychedelic drug/entheogen LSD was first synthesized by the Swiss chemist Albert Hofmann in the Sandoz (now Novartis) laboratories in Basel, Switzerland November 16, 1938.[1] It was not until five years later on April 19, 1943, that the psychedelic properties were discovered.

History of VW Bus http://www.bing.com/images/search?q=...obus&FORM=IGRE

shows not all had the windows around the top

and the VW Bus was not introduced until

The Volkswagen Type 2, officially known as the Transporter or informally as Bus or Camper, was a panel van introduced in 1950 by German automaker Volkswagen as its second car model — following and initially deriving from Volkswagen's first model, the Type 1 (Beetle).