Welsh name are mostly patrionymic meaning it comes from the male line. For example, John the son of Hugh would be John ap Hugh and John's son Evan would be Evan ap John. I imagine Jeremiah was the same way. Jerimiah ap Thomas may have had a son, David ap Jerimiah back before they stopped using that naming system.
The Welsh also during religious reformation times were Methodist and often used Old Testament names like Jeremiah, Isaac or Abraham.
On to R-S11556. I'm going to post what info I have on this page. I haven't tested for it, I'm still at R-L21, but a Nevgen.org predictor which is extremely accurate has predicted mine at S11556. It's a Celtic marker, but it's distribution has led many to believe it was from a Celtic tribe in Denmark and was spread with Danish Vikings.
