Bathrobe's Chinese, Japanese, and Vietnamese language site, by the author's own description "an armchair excursion three fascinating languages of the Orient." I found this website while searching for the names of the days of the week in Japanese, although it also has amusing things like how Harry Potter has been translated into these three languages.

When I first tried to learn the Japanese days of the week, I memorized them using the French names (which are based on the Latin names for planets) and the corresponding Chinese planet names. The two have an uncanny correspondence:

Latin (and French) name for day of week	Corresponding celestial body	Chinese name for celestial body
dies solis	the Sun	日
dies lunae (lundi)	the Moon	月
dies Martis (mardi)	Mars	火 (fire)
dies Mercurii (mercredi)	Mercury	水 (water)
dies Jovis (jeudi)	Jupiter	木 (wood)
dies Veneris (vendredi)	Venus	金 (gold)
dies Saturni	Saturn	土 (earth)

This list of Latin day of the week names translated in Chinese is, in fact, the traditional Chinese (and current Japanese) day of the week system. Yet the traditional Chinese order of the elements is 金木水火土 (gold–wood–water–fire–earth) - it's completely different. So it's obvious that these names were imported. Fingers point to Sumer, Mesopotamia, or ancient Egypt.