Major Hogan in Hail To The Jeep (by A. Wade Wells) said that 'Jeep' is an old Army grease monkey term that was back to at least WWI and was used by shop mechanics in referring to any new motor vehicle received for a test . In recent years (during WW2), the word has been used specifically by the Armored Force but not in relation to the 1/4-ton. Rather it was used in relation to a 1/2-ton command car. Just when this generally used term was specifically applied to the vehicle it now describes is hard to say. Its popularity grows from its general use by the public.
Part of the above is often cited as appearing in a history of Jeep development for the Army's Quartermaster review in 1941. Major Hogan then a Lieutenant wrote two articles for Quartermaster Review during 1941. The first article was one page and it was entitled "The Bug "He said. The word "jeep" is not mentioned at all, however, "bug," "bantam," and "puddle-jumper" are listed. This article appeared in the March / April 1941 issue. The second article was called The Story of the Quarter-Ton – The Army's Smallest Car Known as a "Jeep." In this article there is no reference to "grease monkeys" or even from where the word jeep came from.
There is no notation but since Hogan is listed as a Major, this information may have come from Wells "investigation" (Hail To The Jeep) into the history of the jeep. He sent out little forms to various officers and men in order to find out what they knew about the jeep and its development.