Originally in Scandinavia Tycho/Tyko has got nothing to do with the Greek/Latin name Tycho but it is a latinized form of Tyke, an Old Danish name (older form: Tyki). Tyki was a Danish variant form of the Old Norse name Toki, which derives from the word "tok" (fool, jerk). Toki was used as a short form of Torkel/Torkettil (god Tor "thunder" + helmet) as well.
A Norwegian y-sound is quite similar to a French u-sound and a German Ã¼-sound. You can listen to a Danish y-sound here (which is very close to the Norwegian y-sound, I couldn't find a Norwegian sound...):