This study compares all instances of the usage of the i 以 groupings in the early Edo period Iroha Rhyme dictionaries Zōho iroha zatsuin1 (Extended iroha rhyming dictionary, 1664) and the Kōeki iroha zatsuin kango2 (Kōeki Iroha rhyming dictionary corrected reprint, 1670), and examines the additional contents’ Chinese characters (kanji) and their Japanese pronunciations (wakun). Although the early publication of iroha rhymes is said to have been strongly influenced by the Shūbun inryaku3 (Rime outline, classified and explained), in this study, the Zōho iroha zatsuin and the Kōeki iroha zatsuin kango are compared against the 1612 edition of the Shūbun inryaku. In particular, the later established Kōeki iroha zatsuin kango has further expanded on the additions made in the Zōho iroha zatsuin, and a clear tendency can be observed in which different characters with the same Japanese pronunciation were added.
Iroha rhymes are used to determine rhyme schemes needed to create Chinese poetry using Japanese words (wakun) as a guide. Based on wakun that reflects the meaning of a word, it is helpful to have a large number of kanji with the same wakun pronunciation to select kanji with the same or similar meanings and a suitable rhyme scheme. The additional content in the Kōeki iroha zatsuin kango, which in many cases contains tens of characters with the same wakun, is thought to have been designed to meet this need.
This study also makes a comparison with the “Iroha jishū 4 ,” which is also based on wakun iroha and is contained in the Rakuyōshū 5 , the dictionary of the Jesuit Mission Press in Japan. The left and right marginal notes for each kanji in the Rakuyōshū indicate the Japanese pronunciation most commonly associated with that kanji as a teikun6 (fixed pronunciation) and are clearly differentiated from other pronunciations mentioned under the character notes. While the teikun is consistent with the wakun in the Iroha Rhyme, the degree of consistency is lower with those pronunciations mentioned in the notes. Relatively speaking, it is clear that the teikun is the most stable wakun of its time, but the origin of the pronunciation in the character notes needs further investigation.