"Cinco" means "five" in Spanish; it's most likely a reference to Cinco de Mayo (May 5), a Mexican holiday marking the victory of Mexican troops over French forces in Puebla, Mexico, on May 5; the date is observed in the United States as a celebration of Mexican heritage and pride, but is little known in Mexico itself.
First Scooby-Doo episode to have a female villain in a monster or ghost costume.