Atsutane also researched the origin of languages and letters, such as the ancient Japanese character and Koshihon jikyo (Historical Change of Japanese Syllabary) (Gojuon Giketsu (Historical Change of Japanese Syllabary)) as well as "Shunju Meireki Yoko", "Sanreki Yuraiki" (The Origins of Three Calendar Systems), "Konin rekiunki ko" and "Taiko koeki den" (The Old Calendar of Taihao).
『春秋命暦序考』『三暦由来記』『弘仁暦運記考』『太皞古易傳』他以後古史本辞経（五十音義訣）や神代文字などの言語や文字の起源も研究している。