Got curious, so I looked up the etymology of this word. It comes from the Arabic "al-qadi" meaning "the judge".
"Alcalde (/ælˈkældi/; Spanish: [alˈkalde]), or Alcalde ordinario, is the traditional Spanish municipal magistrate, who had both <i>JUDICIAL</i> and administrative functions. An alcalde was, in the absence of a corregidor, the presiding officer of the Castilian cabildo (the municipal council) and judge of first instance of a town. Alcaldes were elected annually, without the right to reelection for two or three years, by the regidores (council members) of the municipal council." -Wikipedia