Origins of the names for the days of the week

Saturday
Roman: Dies Saturni, Day of Saturn

Sunday
Roman: Dies Solis, Day of the Sun

Monday
Roman: Dies Lunae, Day of the Moon

Tuesday
Roman: Dies Martis, Day of Mars
Norse: Tiwesdaeg 'The day of Tiw',from the Norse Tysdagr

Wednesday
Roman: Dies Mercurii, Day of Mercury
Norse: Wodnesdaeg 'the day of Woden' (Odin), from Norse Odinsdagr.

Thursday
Roman: Dies Jovis, Day of Jupiter
Norse: Thursdaeg 'the day of Thor',from Norse Thorsdagr.

Friday
Roman: Dies Veneris, Day of Venus
Norse: Frigesdaeg 'the day of Freya',from Norse Freyjasdagr.