This article is classified "Fictional"
This word comes from the Middle Icelandic, where part of one volume of "Fizikshritt" has miraculously survived the ages. Since paper had not yet been introduced in Iceland, and all the great minds were too busy arguing about the interpretation of Littlbitzuvstuffmekanik to invent printing, their journals were published in snow and were completely unknown (except in an unreliable Aramaic translation) until an *extremely* lost Bedouin fell into a snow cave in the mid-1950s and looted what he thought were cave drawings. He stupidly tried to peel the snow pages apart, and later merchants used Scotch tape to repair them, so most of the surviving manuscript is in small pieces containing at most a fragment of a word. This makes a complete understanding of Middle Icelandic physics extremely difficult. For example, the best reconstruction of one of the surviving abstracts reads (roughly translated) "It [will] be sh[own] that ... universe splits into different fjords which do [not] communicate with ... whale blubber for dinner pick up cheese for breakfast and go to cleaners on Tuesday." It is hard to believe that the down-to-Earth Icelanders really believed in the Many-Fjords Theory, but we have no independent sources with which to compare these reconstructions. Many of the articles also contain references to a "Wise One" whose "number is 93." Some workers identify this leader with Ludwig Plutonium, and conclude that the beliefs of his cult have existed for much longer than originally suspected. In Icelandic, there is no separate word for "fun" and "wise," however, so another theory is that this was simply an early piece of graffiti and "93" was someone's phone number. (Phone numbers were only two digits, because phones were still luxury items in Iceland during the era of Littlbitzuvstuffmekanik; since as alluded to before, the scientists dealt only with abstract issues instead of transistors, consumer electronics relied on the switching capabilities of very expensive ice flows. The upshot is that the origin of "gedankenexperiment" remains obscure. There are several suggested etymologies. The most commonly accepted is that it is a contracted form of "Gott damm en experiment," which Icelandic fizikists used to shout when trying to perform experiments which were too difficult to do in practice, especially when "massless" pulleys fell on their toes and hurt them. Another widespread belief is that quantum optics experiments had to be done during the dark and cold Icelandic winters to avoid background counts from the sunlight, so most physicists had perpetual sneezes. When you say "gesundheit" to a sneezing Icelander, he replies "gedanken yu," and quantum opticians hence came to be known as the "gedankenfizikists" and their experiments as "gedankenexperiments." By an odd coincidence, the word also looks exactly like the German for "thought experiment," i.e. an experiment which may not be feasible in practice but by imagining which one can (hopefully) come to some interesting conclusions. The root for this word is "denken," to think, and most modern workers incorrectly assume that this is the correct etymology. This is probably because the term was popularized by Einstein, who relied heavily on gedankenexperiments both in his derivation of relativity and in his arguments with Bohr about quantum mechanics.