Perhaps David is a brother to Thomas - all family names.
I have been comparing names and I came across one record (can’t remember now but a BMD and the name Prendergast was written Prender t.
I also knew someone who was Pendergast but often referred to as Prendergast.
Wikipedia shows that they are all variations.
It just seems a bit odd to me that Patrick seems to be the only one registered as Pender which he then uses in his marriage but I can see that it is possible.
