The name Argentina comes from Latin “argentum”, which means silver.
The origin of this name goes back to the first Spanish Conquerors that came to the Rio de la Plata or River Plate. They believed that somewhere upstream the river, native people bathed in silver.
Others, like Sebastian Cabot, bartered or traded provisions for silver trinkets with the Guaraní indians in Asunción, Paraguay, and that inspired him to name the river, Río de la Plata. argentum river or silver river.
Buenos Aires History Tour Argentina