This paper investigates the historical change in the meaning of the word mizumizushii (positive assessment of high moisture). Mizumizushii began to be used in 1880s and continued to be used after the 20th century. In Meiji period, it expressed “(animals and plants) high in moisture, fresh, alive”. In Taisho period, however, it acquired the metaphorical meaning of “(thoughts and feelings) to be fresh, alive”. In Showa period, its metaphorical meaning became a term of appreciation in art. Incidentally, the similar change occurred in mizukusai, a synonym for mizumizushii. Mizukusai appeared at the end of the first half of the medieval period, and originally expressed the literal meaning which is “(sake) to be watery, thin”. By the first half of the early modern period, it developed the metaphorical meaning “(person) not to be frank”. This can be seen as a semantic change from assessment adjectives about moisture content to emotive adjectives about human emotions such as excitement or disappointment. Behind these background are the following values towards water. That is, the positive assessment that “water is always fluid and is the source of life” and the negative assessment that “water is tasteless and odorless”.

Slab-derived fluids are a type of deep-seated fluid characterized by high temperature, high salinity, and a high-CO₂ concentration. They are distinguished from fossil seawater in terms of long-term retention. In this study, the constituents of the microbial community in hot and cold springs from Arima (AR), Kashio (KA), and the Kii Peninsula (KI), which contain slab-derived fluids, were subjected to DNA analysis and the characteristic microbes indicating a contribution of slab-derived fluids to the springs were proposed. Notably, multiple anaerobic thermophiles were detected in the KA cold springs and KI hot springs. These microbes, derived from deep, anaerobic, and high-temperature environments, are considered indicative of slab-derived fluids presence. To enable more comprehensive assessments that incorporate both microbial and traditional geochemical indicators of slab-derived fluids, further case studies and systematic accumulation of comparative data will be essential.