A jib is a sail.Any of various triangular sails set forward of a forestaysail or fore-topmast staysail.In the days of sailing ships, nationality and rigs could often be distinguished by ther jibs. A Spanish ship, for example, had a small jib or none at all. Large French ships often had two jibs and English ships normally had only one.
From ships, the phrase was extended to apply to men. The nose, like the jib of a ship arriving in harbor, is the first part of the person to arrive at a designated place. Figuratively, it implies the first impression one makes on another person.