I wondered if the PD redd and the fish redd are even the same word.



My suspicions are bolstered. The AHD gives a long specific etymology for redd in the sense we know from the Pennsylvania Dutch (http://www.bartleby.com/61/70/R0097000.html) and a terse "Origin unknown" for the fish spawning sense. (http://www.bartleby.com/61/70/R0097050.html)