partisan

Origin

From French partisan, from Italian partigiano (“defender of a party”), from parte (“part”). Doublet of partigiano. Attested in English from the late 15th century in the noun sense of "party adherent", and in related adjective senses from the 16th century. The "guerrilla fighter" sense influenced by Serbo-Croatian partizan, Russian партиза́н (partizán), from the same source. The sense of "guerrilla fighter" is from c. 1690. The adjective in the military sense dates from the early 18th century.