When writing is translated to English and where credit is given, the credit is usually phrased similar to this: “translated from the Japanese by Jay Rubin”.
Why the “the”? Nobody says “I speak the Japanese”. Is the word “language” implicit? That is, should it be read as “translated from the Japanese [language] by Jay Rubin”? Or could the word “original” be implicit? Or is it a holdover from the past when the definite article was used more often? (Was the definite article even used more often in English in the past?) I have no idea; googling this is proving to be difficult.