Is it farther or further?
c.1400, sailer, agent noun from sail (v.). Spelling with -o- arose 16c., probably by influence of tailor, etc., and to distinguish the meaning "seaman, mariner" from "thing that sails." It replaced much older seaman and mariner (q.q.v.). Old English also had merefara "sailor." Applied as an adjective from 1870s to clothing styles and items based on a sailor's characteristic attire.