Thors Day and Jupiter

from Wikipedia http://en.wikipedia.org/wiki/Thursday

The English god Thunor (the Norse Thor), after whom Thursday is named, by Mårten Eskil Winge, 1872

The contemporary name comes from the Old English Þunresdæg, "Thunor's Day" (with loss of -n-, first in northern dialects, from influence of Old Norse Þorsdagr, meaning "Thor's Day"). Thunor and Thor are derived from the Proto-Germanic god Thunraz, god of thunder.

Jupiter's day

In most Romance languages, the day is named after the Roman god, Jupiter who was the god of sky and thunder. In Latin, the day was known as Iovis Dies, "Jupiter's Day". In Latin the Genitive or possessive case of Jupiter was Iovis/Jovis and thus in most Romance languages it became the word for Thursday: Italian giovedì, Spanish jueves, French jeudi, Catalan dijous, and Romanian joi. This is also reflected in the p-Celtic Welsh dydd Iau.

In most of the Indic languages the word for Thursday is Guruvar — var meaning day and Guru being the style (manner of address) for Bṛhaspati, guru to the gods and regent of the planet Jupiter.

The astrological and astronomical sign of the planet Jupiter () is sometimes used to represent Thursday.