As represented by such words as “iːʧi (breath), uːʃi (mortar), wuːki (tub)” in the modern Shuri dialect, many ‘northern’ Ryukyuan systems located in the areas from Amami-Ōshima down to the Okinawan main island exhibit lengthened vowels in the initial syllables of C-Keiretsu (Class C) disyllabic nouns in the Keiretsubetsu-goi. It was first pointed out by Hattori (1932) that the lengthening should have occurred due to some reason related to accent.

Following Hattori (1932)'s assumption, but contrary to Hattori (1979)'s hypothesis that the vowels were already long at the stage of Proto-Japanese-Ryukyuan, this paper argues that the vowel lengthening occurred at the stage of Proto-Northern-Ryukyuan, stating that the cause of the lengthening is ascribed to its accentual system. More specifically, the paper proposes that the vowel lengthening took place in order to make a clear-cut distinction from a similar pattern (which is Class A) in the same system, and that it took place in order to make the tonal pattern similar to the one of the trisyllabic nouns of the same class (Class C) in the same system.

In the history of the study of Japanese grammar, the influence of Western grammar books on the understanding of Japanese case marking can be found in many grammar books following ever since the Edo Period Gogaku Shinsho by Tsurumine Shigenobu. This paper takes the Dutch grammar book precursors to this type of grammar books as a context in which to compare Yoshio Shunzou's Rokkaku Zenpen (1814) and Fujibayashi Fuzan's Oranda-goho-ge (1812), in order to shed light on their respective understandings of case marking in the Japanese language (also known as teniwoha). Although there are commonalities in how the function of case is interpreted in both works, special characteristics appear in each text's treatment of case marking system. In particular, it can be seen that in Rokkaku Zenpen the interpretation of expressions unmarked for case owes much to Motoori Norinaga's analysis of these as examples of the category “tada”. By examining both books understanding of case, this study throws the influence of Kokugaku (Japanese philology) into relief, and as it traces the connection from Rangaku (Dutch language learning) on case marking to Tsurumine's Japanese case research, it clarifies the understanding of Japanese teniwoha by Dutch language scholars in the history of Japanese language studies.