The only free and comprehensive online etymological dictionary of the Spanish language
mal (Adverb, Noun) "badly;" "bad," "evil"
12th cent. From Latin male "badly," from malus "bad" (see malo).
Indo-European
Romance
Portuguese mal, Catalan mal, French mal, Italian male, Sardinian mabi
Corominas, J. & J. Pascual. Diccionario crítico etimológico castellano e híspanico. 6 vols. Madrid: Gredos. 1991-1997.
Real Academia Española. Diccionario de la lengua española. Online. 23rd ed. Madrid: Espasa Calpa. 2014. http://www.rae.es/.
Sihler, A. New Comparative Grammar of Greek and Latin. Oxford University Press. 2008.