Etymology of Peru

The word Peru is derived from Birú, the name of a local ruler who lived near the Bay of San Miguel, Panama, in the early 16th century.[4] When his possessions were visited by Spanish explorers in 1522, they were the southernmost part of the New World yet known to Europeans.[5] Thus, when Francisco Pizarro explored the regions farther south, they came to be designated Birú or Peru.[6] The Spanish Crown gave the name legal status with the 1529 Capitulación de Toledo, which designated the newly encountered Inca Empire as the province of Peru.[7] Under Spanish rule, the country adopted the denomination Viceroyalty of Peru, which became Republic of Peru after the Peruvian War of Independence. source(wikipedia)