i'm pretty sure i wish i could find more history about it that the the toponym river plate is a relative neologism coined in the british empire esp in england perhaps as little as a century or so ago you're surety is misplaced the british have been calling it river plate since drake with the barest minimum of research i counter your assertion with the fact that a book entitled a narrative of the operations of a small british force under the command of brigadier general sir samuel auchmuty employed in the reduction of monte video on the river plate a d by a field officer on the staff illustrated with a plan of the operations was published in see samuel auchmuty