The names of the days of the week in Germanic and Romance languages are pretty interesting because they were borrowed several times with people just substituting their own equivalent gods in as a calque.
It started in Ancient Greece, where the days were known as:
- Sun’s day (ἡμέρα Ἡλίου)
- Moon’s day (ἡμέρα Σελήνης)
- Ares’ day (ἡμέρα Ἄρεως)
- Hermes’ day (ἡμέρα Ἑρμοῦ)
- Zeus’ day (ἡμέρα Διός)
- Aphrodite’s day (ἡμέρα Ἀφροδίτης)
- Cronos’ day (ἡμέρα Κρόνου)
supposedly named after each heavenly body that “presided over the first daylight hour of each day.” This has been lost in modern Greek which now mostly just names its days by number.
The Romans gradually adopted the same system, and named their days:
- Sun’s day (dies Sōlis)
- Moon’s day (dies Lūnae)
- Mars’ day (dies Martis)
- Mercury’s day (dies Mercuriī)
- Jupiter’s day (dies Iovis)
- Venus’ day (dies Veneris)
- Saturn’s day (dies Saturnī)
with them replacing the Greek gods with their closest equivalents, eg Mars and Ares are the Roman and Greek gods of war respectively, Mercury and Hermes the messengers, Jupiter and Zeus the kings of the gods and the gods of thunder, Venus and Aphrodite the goddesses of love etc.
These forms are still clearly visible in most Romance languages - lundi/lunes/lunedì, mercredi/miércoles/mercoledì etc. The only difference is the weekend, which would later be named after the Sabbath and the Lord (Dominicus) instead of Saturn and the Sun.
Portuguese - as did modern Greek - opted instead to name its days by numbers.
The Germanic peoples then also borrowed the Latin system they’d been introduced to and calqued it once again with their own equivalent gods, thus:
- Sun’s day (Sunday)
- Moon’s day (Monday)
- Tiw’s or Tyr’s day (Tuesday)
- Wodan’s or Odin’s day (Wednesday)
- Thor’s or Donar’s day (Thursday)
- Frigg’s or Freya’s day (Friday)
- Saturn’s day (Saturday)
Saturday is the only one to retain its Roman origin.
These are all the rough equivalents of the Roman gods (the matches aren’t always exact but they’re what was deemed close enough/appropriate at the time), eg Thor is the god of thunder (like Jupiter and Zeus), Freya the goddess of love (like Venus and Aphrodite), etc. They’re all literally direct translations of each other with the local gods subbed in, and with the exception of the languages that changed “Wednesday” into something resembling “middle of the week” (German Mittwoch, Icelandic miðvikudagur etc) they’re mostly the same across all the Germanic languages.
I just thought it was pretty cool the way the exact same concept travelled across multiple cultures like that. ^^