I have been offhandly researching my surname "Ikerd" for a while and discovered my ancestor listed as "Peter Eigerdt" who changed his name to "Ikerd" in 1745.The resulting lines changed their surnames to "Ikerd & Ikard".
I too have been trying to find Eigerdt in Germany and have only found one "hit" on a search engine on a German web site.It is a woman who works in a German company and unfortutanely its all written in German.
I have attempted to contact her but have not received any response.
The only other thing I can give you a vague "german surname" lesson I learn while digging around.Apparently the end other the spelling of the name means different things such as a woman could have a difeernt spelling than a man from the same family.So... It looks as if we "Ikerds and Ikard's" could all be from the same lineage, but it's looks to be difficult search at best.
Sounds like a german professor might be able to shed some light on the meaning and how the name came about...