To distinguish himself from the many Pero Hernándezes in New Spain, we believe that this expeditionary added "de Guadalajara," meaning "from Guadalajara." Two pieces of information to support this assumption involve Viceroy Mendoza. First, the Mendoza clan headquarters was in Guadalajara, Spain and Mendoza surrounded himself with individuals who would be loyal to him, individuals who were natives of property held by the Mendozas. Second, there was a Pedro Hernández among the members of the viceroy's personal guard. There were two other expeditionaries, Saldaña and Soto, also from Guadalajara and also in the personal guard. Otherwise the documentary record for this expeditionary is nearly non-existent. Pero mustered into the Expedition as a footman, the same position Pedro Hernández held in the guard.
AGI, Justicia, 259, pieza 2 [visita a don Antonio de Mendoza] [copy of document from January 2, 1538 lists Pedro Hernández footman in Mendoza’s personal guard (this could be him if he is from Guadalajara and serving in the guard with Saldaña and Soto also from Guadalajara)
1540, Feb: Muster in Flint & Flint, Documents, Document 12 [arquebus, sword, dagger, footman]
?AGN, Instituciones Coloniales, GD72, Real Audiencia, Mercedes, vol.3, exp.48bis, 1550 [fols. 22v – 24r: List of payments of ayuda to 95 persons who participated in the armada to Perú; the list includes: seven Genoese and numerous other foreigners (Flemings, Germans, Italians); Pedro Hernández (30 pesos de minas); a Juan Pérez (25 pesos); a Juan Fernández, artillero (40 pesos); Juan Fernández, ladrillero, piloto (80 pesos); an Alonso González (25 pesos); a Juan Gallego (25 pesos); a Juan Pérez de Navarra (25 pesos); a Diego Sánchez, tonelero (25 pesos)]
Piferrer, Nobiliario, 3:94, #1265 [Hernández name from Córdoba; went to Galicia; el origen de esta casa y apellido se cree muy ciertamenta que es tomado del rey don Fernando, y derivado de este nombre en Fernández and alterado despues en Hernández; escudo of sinople and a gold castle de cuyas almenas sale un brazo armado con espada and 2 lions del mismo metal empinantes al castillo, bordura de gules and 8 gold stars]