The source of my interest is likely obvious. The name itself is much more common in Belgium than in Netherlands though my ancestry on that side is from Schiedam, outside Rotterdam. I include German as well as Dutch because we believe that an ancestor moved to South Holland from Stuttgart in the mid 16th century.
Of course growing up the obvious similarity of the name to the gherkins pickle was too obvious to be missed. The question is whether that resemblance is or is not coincidental.
Pronunciation of the initial syllable of the name in Schiedam, where my father and his father grew up, is done with a long-e sound and with the "G" rolled far back in the throat, so soft as to almost be an "H" sound. The mouth is open moderately wide in an oval shape and the tongue pushed forward. I'm not a linguist by any means, but managed to master this sound in my 30's. This information perhaps will assist in filtering some of the possible etymology.