Mendoza is a Basque surname, also occurring as a place name.
The name Mendoza means "cold mountain", derived from the Basque words mendi (mountain) and (h)otz (cold) + definite article '-a' (Mendoza being mendi+(h)otza). The original Basque form with an affricate sibilant (/ts/, Basque spelling /tz/) evolved in Spanish to the current form.
Originally the noble family line bearing the surname was based in the castle of the same name, not far from Vitoria-Gasteiz, Basque Country, where it still stands out. However, one of the family branches comes from Laudio, 50 km away to the northwest from Vitoria-Gasteiz. The family got involved in the medieval bloody War of the Clans. Not only that, the house of Mendoza set up close ties with Castile since the High Middle Ages, with its members participating in their civil wars and the Castilian expansion south. They got wider renown after their involvement in the conquest of America after 1492.
In Erandio, a baserri exists with the same name. Its original name "mendotza" developed to "mendontze" in the 1890s, "mendoche" in the 1920s, "mendotxe" in the 1980s to the restored original of "mendotza" being the current.