Say the days aloud and you are speaking the names of gods, planets, and a pair of celestial bodies. Sunday is the Sun's day. Monday is the Moon's day. Tuesday belongs to Tiw, Wednesday to Woden, Thursday to Thor, Friday to Frigg, and Saturday to Saturn. Every one of the seven traces back through Old English to Roman and Norse mythology.
Sunday and Monday the Sun and Moon
Start with the two you can see. Sunday comes from the Sun's day. Monday comes from the Moon's day. Both are direct translations from Latin, where the days honoured the sun and moon as celestial bodies. The Old English forms were Sunnandæg and Mōnandæg. No gods, no substitution. Just light and tides.
Tuesday Tiw's Day
Tuesday is named after Tiw, also spelled Týr, a god of war and justice. The Anglo-Saxons matched him to the Roman Mars. The Old English name is Tiwesdæg. In French, the parallel is mardi, straight from Mars. So Tuesday carries a war god in both language families, just wearing a different name.
Wednesday Woden's Day
Wednesday is Woden's day. Woden is the Anglo-Saxon name for Odin, the chief god of Norse myth, equated with the Roman Mercury. The Old English form is Wodnesdæg. In French, the day is mercredi, from Mercury. Wednesday sits in the middle of the week, and its name comes from a god of wisdom, poetry, and travel. Fitting for a midpoint.
Thursday Thor's Day
Thursday is Thor's day. Thor was the Norse god of thunder, equated with the Roman Jupiter. The Old English name is Þunresdæg, where Þunres means thunder. So the answer to why it is called Thursday is the thunder god. In French, the day is jeudi, from Jupiter. Thursday lands late in the workweek, and its name comes from a powerful sky god.
Friday Frigg's Day
Friday is Frigg's day, named after the Norse goddess Frigg, sometimes associated with Freya. She was equated with the Roman Venus. The Old English form is Frigedæg. In French, the day is vendredi, from Venus. Friday is the last workday for many, and its name comes from a goddess of love and fertility.
Saturday Saturn's Day
Saturday is Saturn's day. Saturn was a Roman god of agriculture and time. This is the only day name that kept its Roman god directly. No substitution. The Old English form is Saturnesdæg. In the Romance languages, the day also comes from Saturn: French samedi descends from Saturni dies. Saturday is a direct link to ancient Rome.
The Norse Gods and the Roman Connection
The pattern is clear. The Romans named the days after the seven planets they knew: Sun, Moon, Mars, Mercury, Jupiter, Venus, Saturn. When Germanic tribes adopted the seven-day week, they swapped in their own gods, matching attributes. Here is the full list:
- Sunday: Sun (Roman) / Sun (Germanic)
- Monday: Moon (Roman) / Moon (Germanic)
- Tuesday: Mars (Roman) / Tiw (Germanic)
- Wednesday: Mercury (Roman) / Woden (Germanic)
- Thursday: Jupiter (Roman) / Thor (Germanic)
- Friday: Venus (Roman) / Frigg (Germanic)
- Saturday: Saturn (Roman) / Saturn (Germanic, kept)
The Romance languages kept the Roman planet names. French uses mardi (Mars), mercredi (Mercury), jeudi (Jupiter), and vendredi (Venus). If you speak a Romance language, the days still refer to the original Roman gods. In English, only Saturday keeps that Roman link.
How the Names Changed Over Time
The Old English forms evolved into modern English through centuries of spoken use. Here is the trail:
- Tiwesdæg became Tuesday. The dæg part became day, and Tiwes shortened to Tues.
- Wodnesdæg became Wednesday. The d was dropped, and Wodnes became Wednes.
- Þunresdæg became Thursday. The Þ (thorn) became Th, and unres became urs.
- Frigedæg became Friday. The ge sound was lost, leaving Fri.
The names stuck because they were tied to everyday life. No decree imposed them. People just kept saying them, week after week, until the old forms wore smooth.