Sorry, also here
Ilse is ultimately a diminutive from
Elisabeth:
According to the following site, the
German town Ilsenburg originally was called "Elysynaburg"
http://www.vg-ilsenburg.de/staticsite/staticsite.php?menuid=64&topmenu=64&keepmenu=inactiveSo this would mean, that
Ilse is from Elysyna. I found given names Elysyna and Elysyn, Elysyn also in use as a surname. I did not find the meaning and origin, but it's probably a form of
Elise, which is a short form of
Elisabeth.