It's primarily a surname. Here's the meaning of the name of a town called Zell, all I could find...
The town Zell im Wiesental owes its origin to the monks of St. Fridolin of the monestry Bad Säckingen. The martyr Fridolin set down in this area between 550 an 650. Around 1000, first of all, the monks were building a "Cella", a small, wooden chappele. In addition to this chapel, they built living accommodations one or several cells- this is the origin of the name of the town.
I think Zelle also means "cell" or "cabin" in
German.