Allegheny River -- "beautiful water".
Monogahela River -- "steep banks along the water".
Ohio River -- "fair waters"
Youghiogheny River -- "circuitous or winding stream"
Susquehanna -- "Long, Winding River"
Juniata River -- "a projecting rock" or "Standing Stone"
Shenango River -- "bull thistles"
Kishacoquillas Creek -- "The snakes are already in their dens"
Tuscarora Creek -- "hemp gatherers"
Ohiopyle -- "water whitened by froth"
Pymatuning Creek -- "crooked mouthed man's dwelling place"
Kinzua Creek -- "they gobble"; referring to wild turkeys frequenting the watershed
Punxsutawney -- "gnat town"
Many more (PDF)