Walter Henry Medhurst
The spelling and pronunciation "yen" is standard in English because when Japan was first encountered by Europeans around the 16th century, Japanese () and () both had been pronounced and Portuguese missionaries had spelled them "ye". By the middle of the 18th century, and came to be pronounced as in modern Japanese, although some regions retain the pronunciation. Walter Henry Medhurst, who had neither been to Japan nor met any Japanese people, having consulted mainly a Japanese-Dutch dictionary, spelled some "e"s as "ye" in his "An English and Japanese, and Japanese and English Vocabulary" (1830). In the early Meiji era, James Curtis Hepburn, following Medhurst, spelled all "e"s as "ye" in his "A Japanese and English dictionary" (1867); in Japanese, "e" and "i" are slightly palatalized, somewhat as in Russian. That was the first full-scale Japanese-English/English-Japanese dictionary, which had a strong influence on Westerners in Japan and probably prompted the spelling "yen". Hepburn revised most "ye"s to "e" in the 3rd edition (1886) to mirror the contemporary pronunciation, except "yen". This was probably already fixed and has remained so ever since.