Hi, A lot of us have wondered about its origin.I don't think anyone has ever had a real theory on it.I know my husband's name evolved here in the US from Codner to Cardner.My Geiger line went from Gyger to Giger to Gieger to Geiger.
My Colliers are found on a Florida census as Coliere and Colyer.
My Murphys were Murfee, Murphee.
That is a good question, and none of us have figured it out. Sydney