Early 17th century; earliest use found in Francis Bacon (1561–1626), lord chancellor, politician, and philosopher. From post-classical Latin alterant-, alterans, present participle of alterare alter. In use as noun in sense B. 1 after French altérant alterative medicine, use as noun of altérant alterative, use as adjective of present participle of altérer. In use as noun in sense B. 2 after post-classical Latin alterant-, alterans, use as noun of present participle of alterare.