A swedish battle

I want some help with the name of a place where a battle once was
fought. Let me give you the history behind it all before I ask.

In 1210 there was a battle between two kings, both wanted the swedish
throne. The place where they met is called Gestilren in old texts.
Somehow, the knowledge of the place got lost through the centuries and
all we know today is the name of the place, not where the battle was.
Now, there are two contenders to the spot and both of them look like
the old place name but not fully.

The first place name is Gästillen. The other is Gästre. Both these
places have been renamed since they first were named in the church
logs. What I want to know is which of these two names are closest
etymologically to the old Gestilren. Both places have their respective
followers and a really nasty discussion erupted on a history forum here
in Sweden this spring.

To let you know about Gestilren as it is told in the sources from the
time: In the oldest source, written in latin about ten to fifty years
after, it is said that "they have fought a war on Gestilren again".
Notice the the on, not at or in. The oldest swedish source about the
battle tell us that Gestilren is located between a place called Lenum
and Dal. The first contender, Gästillen, is located on a hill between
two small villages called Dal and Lena. The other contender, Gästre,
doesn´t have that geographical edge but there is a legend of a tussle
between kings at this place, which can not be said about the first
contender.

There you have it. I can say that nobody knows what Gestilren means and
where the name comes from.

Carl Hult