E. Cobham Brewer 18101897. Dictionary of Phrase and Fable. 1898.
Feather Ones Oar (To).
To feather an oar is to turn the blade parallel with the surface of the water as the hands are moved forward for a fresh stroke. (The Greek pteron means both an oar and a feather; and the verb ptero, to furnish with oars or with feathers.) The oar throws off the water in a feathery spray.
He feathered his oars with such skill and dexterity.