man-of-warn.

man-of-war (n.)late 14c., "a soldier," from man (n.) + war. Meaning "vessel equipped for warfare" is from late 15c. Man in the sense of "a ship" is attested from late 15c. in combinations (such as merchantman). The sea creature known as the Portuguese man-of-war (1707) is so called for its sail-like crest.