Each day of the seven day week held a special significance to a god. Sunday was the day sacred to the Sun, Monday the Moon, Tuesday Tyr, Wednesday Odin, Thursday Thor, Friday Frigga, and Saturday Loki. The name of each day sounds fairly similar to its corresponding god, with the exception of Saturday, which is often mistakenly assumed to be named for the Roman god Saturn.
Saturday, the final day of the week, was originally known as Laugardag (formed from Loki’s name, but it translates to wash-day). When adapted to English, the day did in fact maintain its connection to Loki. The word Saturday is based on Sataere (the thief in ambush). This is simply another one of Loki’s names, used when referring to Loki as a god of agriculture (each of the gods presided over several different aspects of the universe, and Loki was no exception). So, although few know of it, the final day of the week is still named for Loki.
Incidentally, I’ve seen a lot of campaigns online prompting people to begin calling Saturday “Lokisday”. Most people have no idea Saturday is named after Loki, so Loki’s significance to the day is forgotten. This campaign to call Saturday Lokisday seeks to reinforce Loki’s connection to the day. This is an interesting idea, and I will definitely attempt to use Lokisday as often as I can remember.