Shimatani 【島谷】5 The Japanese surnames etymology dictionary.
Ibaraki-ken Omitama-shi · Toukyou-to . Ibaraki - ken Omitama - shi In Ogawa Ibaraki - ken tells that he changed his name from Yokosuka 's surname in around 1877 to avoid conscription in Naka - gun. There is also a story that the meaning is unknown in the same place. 横須賀 reference.