The names are used in Japan. Some of these names (e.g., "Strike Gold") conjure up an old-school Americana. This is intentional. Japanese denim brands (who now make these shirts as well) are very reverent of pre-1960s Levis.
They use the English names in Japan. If you google for the Japanese official websites for these brands or even their products on rakuten.co.jp you'll see the brand names in English.