I found your post very interesting, but I really don't believe I can be of much help. We have a couple of lines of Yunkers in our area of northern Indiana & southern Michigan of which my husband is descended through his maternal line. Our earliest Yunker is Hans Jacob b. 8-nov-1760 in Jagensdorf Switzerland married to Elizabeth Aberhard. The odd thing about it is that his grandmother Yunker was a Leu. I have had contact some time ago with a Leu that was in the Chicago area. Both families came from Switzerland however. If you think there might be any connection, I'd be glad to give you further information.