Jib

Generally, a jib's most crucial function is as an airfoil, increasing performance and overall stability by reducing turbulence on the main sail's leeward side.

[3][4] From forward to aft, these sails are called: The first two were rarely used except by clipper ships in light winds and were usually set flying.

The phrase alludes to the maritime practice of identifying far-away ships by noting the "cut" (general shape and configuration) of their sails to determine their status as friend or foe.

One such report from the Naval Chronicle (1805)—"we perceived by the cut of their sails, then set, that they were French Ships of War"—is often cited as an early inspiration for the idiom.

[5][6] Sir Walter Scott used the expression to denote approval in the 1824 novel St. Ronan's Well: "If she disliked what the sailor calls the cut of their jib".

[7] John Russell Bartlett later defined the idiom in his 1848 Dictionary of Americanisms as "The form of his profile, the cast of his countenance".