Origin of the names of the days

The names of the days are in some cases derived from Teutonic deities or, such as in Romance languages, from Roman deities. The early Romans, around the first century, used Saturday as the first day of the week. As the worshipping of the Sun increased, the Sun's day (Sunday) advanced from position of the second day to the first day of the week (and saturday became the seventh day).

Sunday: The name comes from the Latin dies solis, meaning "sun's day": the name of a pagan Roman holiday.

Monday: The name comes from the Anglo-Saxon monandaeg, "the moon's day". This second day was sacred to the goddess of the moon.

Tuesday: This day was named after the Norse god Tyr.

Wednesday: The day named to honor Wodan (Odin).

Thursday: The day named after the Norse god Thor.

Friday: The day in honor of the Norse goddess Frigg.

Saturday: This day was called dies Saturni, "Saturn's Day", by the ancient Romans in honor of Saturn.


Source: http://www.pantheon.org/miscellaneous/origin_days.html