The story
The air arsenal's roots go back to 1869 when the Imperial Japanese Navy (IJN) established a naval arsenal at Yokosuka, about 13 miles south of Yokohama on Tokyo Bay. The arsenal provided ship building, repair and replenishment to the Japanese Navy. It was also a storage depot where munitions and other assorted supplies were brought as they were purchased.
When a number of foreign aircraft were purchased for evaluation, the Navy brought them to the arsenal for processing. The arsenal assembled the aircraft from their shipping boxes, and when assembled, they were flown by the pilots who had been sent abroad for flying lessons and evaluate the aircraft flown.
Modifications to these aircraft were done as weaknesses were found, or when an improvement was incorporated. To facilitate this work, the IJN established the Aeroplane Factory, Ordnance Department at the arsenal's torpedo factory in May 1913.
The next year, the first acronym was used was Yokosho, a contraction of Yokosuka Kaigun Kōshō (Yokosuka Naval Arsenal). The arsenal was renamed Kaigun Kōkū Shiken-sho (Naval Establishment for Aeronautical Research) in December 1919. The name Kaigun Gijutsu Kenkyūsho (Naval Technical Research Institute) was assigned by April, 1923, when the arsenal was moved to Tsukiji with several other Naval support units. The entire Tsukiji facility was destroyed in the 1923 Great Kantō earthquake. Several names were used when the navy began establishment of the arsenal. Research was started again in 1924 when several aircraft were evaluated. Under the command of the newly formed Naval Air Headquarters, the Kaigun Kokusho (Naval Air Arsenal) was formed at Yokosuka on 1 April 1932. A large amount of draftsmen and Designers were transferred from the Hiro Naval Arsenal, ending aircraft production there.
From Wikipedia’s article on Yokosuka Naval Air Technical Arsenal, shared under CC BY-SA 4.0.3