It's a very German name.
Many names we tend to consider Jewish, are German, and are used by German gentiles. We consider Rosenberg a "Jewish name," but then there was Alfred Rosenberg, the Nazi.
Glaser is the German word for glazier, i.e. a person who blows glass. If you look up U.S. history, a bunch of Germans came to the U.S. in the 1700's who were Protestant.
In the 70's there was a country musician named Tompall Glaser. I think his brother Jim was a slightly less successful country musician. Both gentiles.
Also in the 70's, there was Paul Michael Glaser who was on the show Starsky & Hutch, who was Jewish. I wonder if he's why people think of it as a Jewish name.
There was also a Nobel Prize winner in Physics whose name was Donald Glaser who was Jewish.
But in Germany, Austria, and Switzerland it wouldn't be considered Jewish.
so a German name can’t also be Jewish?