In English, the fourth weekday is named after Thor, nordic and germanic god of thunder and lightning. This is also the case in Swedish and Danish (Torsdag). The German and Dutch names refer to Thor's major attribute - thunder ( Donnerstag, Donderdaag). In the Latin languages, this day is called after Jupiter/ Jove - jueves (Spanish), jeudi (French), giovedi (Italian) - whose attributes also included control of thunder and lightning.
Variants of the god's name in the Germanic languages include Thunnor, Donar. In norse mythology, Thor was one of the most powerful deities. He was usually portayed as a huge strong man with a red beard and hair and "eyes of lightning..... He even surpassed his father Odin in popularity because, contrary to Odin, he did not require human sacrifices." Encyclopedia Mythica. His adventures, especially his battles with giants, featured prominently in the prose Edda, written by the 12th/13th century Icelandic historian, Snorri Sturluson.
The son of Odin and a giantess, Jord, Thor protected Asgard and Midgard (heaven and earth) from various forms of evil, usually fighting against the attacks of giants Wikipedia. In the Edda, Thor's greatest enemy was the Midgard Serpent, Jormungand. He will kill the serpent at Ragnarok (the time of the end of the world) but will die from its poison. During thunderstorms, Thor rode across the sky in a chariot drawn by goats.
His magical possessions were the belt, Megingjard - which doubled his already great strengththe war hammer, Mjolnir - which produced thunder and lightning when he threw it and returns to him after being used. Thor needed iron gloves to lift Mjolnir, which could flatten mountains and allowed him to kill giants. A hammer shaped pendant was often worn by nordic tribes to show devotion to Thor. (See Wikipedia article on Mjolnir.)
There are many stories about Thor in the Poetic and Prose Edda. The story about how Thor got his magical items features his companion Loki, another major norse god. In norse mythology, Loki was a "trickster" god of fire and magic, who could change shape. He could be cruel, malicious and treacherous and often fought the other gods. Loki was caught by the frost giant Geirrod, when Loki was flying in the shape of a hawk. He agreed to help Geirrod trap Thor, by leading him into Geirrod's castle. However, the giantess Grid warned Thor and gave him the iron gloves, the belt and a staff, so that Thor was able to kill Geirrod and all other frost giants.
Thor's attributes and mythology were used as focus for the Marvel comic character created in 1962 by Stan Lee, Jack Kirby and Larry Lieber. Thor had his own series of comics, as well as being a member of the Avengers. Thor's main enemy in the comics was Loki, with the comics focusing on the treacherous aspects of the character.