Saturday is the only day of the week that retained its Roman origins in the wake of the English invasions of the Angles and Saxons. This may have been because there was no Norse God to roughly correspond to the Roman God of Time and the Harvest, Saturn. The Anglo-Saxons simply adapted the Roman, "dies saturni", making it saterdaeg.
Besides his ownership of a day of the week. Saturn presided over a Roman festival known as Saturnalia. It was a celebration of the harvest, but it was also a time when life was turned on its head. Crimes committed on these days often were not punished; masters frequently waited on their servants; and revelry was taken to excess.
Saturday is the seventh day of the week and as such was the day upon which the Hebrew God commanded his people to rest. Through to our modern age Jews keep Saturday holy as the Sabbath - quite a contrast to Roman practices.
Saturdays are a popular day for weddings in Christian cultures because it is typically a day free from work and it preceedes another day of rest - Sunday. (In Moslem countries - for a similar reason - Thursdays are a prefered day for weddings.)
Before the advent of the 5 day work week (which began to come into vogue in the early 1900's) Saturday was much like Friday, in that it was the final workday before the day of rest. It is interesting to note that before the last few generations the long work week was standard and endured without complaint from most workers. In our own time the 5 day work week is often depicted as long and difficult.
As the centuries pass conditions shall change the nature of these days of the week. Already, the strict notions of apropriate behavior upon the Sabbath have changed. The idea of Monday holidays to create 3-day weekends is a relatively new invention. What change shall come next to vary our own perspective of the endless cycle of the week?