mid-18c., lively Spanish dance, the word of unknown etymology [OED says "alleged to be of negro origin"], of uncertain origin. Perhaps related to fado (Watkins traces both to Latin fari "to speak"); fado is lovely but not lively, so perhaps the link, if any, is thematic. By extension in American English, "any noisy entertainment."[fandango etymology, fandango origin, 英语词源]