He said the Greek (modern, not ancient) name -- Δευτέρα (Deftéra), which has nothing to do with moons, but means "second day". Obviously this only makes sense in a Christian context which starts the week on Sunday. Monday is "first day" (星期一) in Chinese, for example.
Christian context is a bit fuzzy here. On one hand, Monday is called the same in Hebrew (יום שני [yom sheni] = "second day"). On the other hand, Russian "вторник" [vtornik] ≈ "second" is Tuesday, same in other Slavic languages.
