The sort-of compound words ji-nashi, ji-mori, and ji-ari all begin with the term ji. In the context of shakuhachi, ji can refer to any substance that’s applied and adheres to the inside of the bamboo bore which augments the geography with the intention of affecting play-ability, i.e., pitch, tone, and range. Looking at the second part of these words, nashi means “without”, mori is “a portion”, and ari means “to have (jinashi 地無し, jimori 地盛り, jiari 地塗り).
However, the term ji excludes lacquer or urushi because it’s not seen as being a form of tuning. Furthermore, strictly speak, ji refers to jinoko which is a fine stone powder that’s mixed with urushi lacquer to form a plaster. Jinoko plaster is used to create the base layer on the wood of lacquerware. Shakuhachi makers undoubtedly learned their urushi skills from lacquerware artists.
Historically, the first types of shakuhachi were jinashi, however, they were simply called shakuhachi because they were the only type until the 20th century. Contrary to popular belief, ji was used in the bore of some shakuhachi during the Edo period (1603 and 1868). However, it’s unclear as to whether or not it was used to intentionally augment the sound (note that jointing shakuhachi was also done during the Edo period). Around the end of the 1800’s, Araki Chikuo, AKA Kodo II (1823-1908) is credited as the first shakuhachi maker to systematically apply small amounts of ji to his shakuhachi with the intention of affecting the sound (he did not apply ji to all of his shakuhachi, so it seems he used it only when he felt they would benefit). This approach of using a “portion” or small amount of ji has become known as jimori, though this term appears to be very recent. Chikuo’s students took his idea much further by applying ji to the entire inner surface of their shakuhachi, thus the jiari shakuhachi was born.
In short order, the jiari became the new standard of the 20th century. This shift made jinashi largely relics of the past. This is reflected in the fact that jiari are often just called shakuhachi in Japan to this day, not “jiari”. However, jinashi and jimori are increasingly more popular, enjoying a full fledged renaissance in recent times.
Additionally, there are subcategories of jinashi such as hochiku (法竹 aka hotchiku or hocchiku) and Kyotaku. Hochiku were created by Ishibashi Gudo at the request of master Watazumi (1910-1992). They tend to be much longer and larger on the inside than previous shakuhachi in history, such as those used by the Komuso monks of the Edo period. Invented by Nishimura Koku, the Kyotaku are also longer bass or choukan shakuhachi which follow certain specific criteria, such as having all the holes in a straight line and of a smaller size. Lastly, these longer bass shakuhachi inspired various “spiritual successors” such as Ken LeCosse’s very large/wide Taimu or “big nothing” shakuhachi.