Please regard this as a non-scientific contribution to the topic of origin of name of Cowpen!
Just like cowpenexile I remember Father Dunne giving us local history info from his pulpit- this in mid-late 1940s. But in my memory he declared that Cowpen was named after Copenhagen. I think us kids liked this source better than cowping and salt pans.!
I have mislaid my handy book " Goodwife Hot- The History of Northumberland in its Place Names"
And unfortunately my book " A Dictionary of English Place-Names" by A.D Mills, has no entry for Cowpen, but includes one for Cowpen Bewley, near Stockton-On-Tees. Cowpen pronounced same as Cowpen near Blyth.
__________________________________
" Cowpen Bewley, Cleveland, "cupum" c1150 = place by the coops or baskets ( for catching fish)
Old English cupe "
Before Cowpen and Blyth merged in 1907 , Cowpen's territory covered the River Blyth's riverside from Bebside to just behind Blyth modern day bus station.