I found this interesting, but the names of the days of the week match up in both Japanese and English, perfectly reflecting the names of the planets and their corresponding gods, and in turn the actual names of the days themselves.
In addition, a lot of the Greek and Roman words are used as roots in English as well. Greek, as usual, for scientific and higher-level vocabulary, and Roman/Latin for more common words. This seems to reflect, interestingly, the use of Chinese-based words in Japanese as higher-vocabulary versions of native words.
Some examples in English:
- Helios: Helium, heliocentric, heliotrope, perihelion
- Sol: Solar system, solarium, solstice, south
- Selene: selenography (study of the moon), sultry, swelter
- Luna: lunar, lunatic
- Moon: menopause, month, menstrual, meniscus
- Mercury: mercurial, market, merchant
- Odin/Woden: wood
- Aphrodite: aphrodisiac, april
- Ares: ire
- Mars: march, martial
- Jupiter: father
- Thor: thunder
- Chronos: chronological, anachronism, chronic, chronicle, crony
- Pluto: plutocracy
- Terra: territory, terrestrial, terraform
- Gaia: geography, pangea, apogee, perigee
It makes me wonder what the old names of the days of the week were, before they took on the current Western-influenced ones, or even if the concept of a week or weekday existed, say pre-Meiji era…
UPDATE:
Looks like the order of the days of the week may have gone back further than this. The above is still the derivation of the English words, but the order and name preceded all that: http://www.cjvlang.com/Dow/dowjpn.html