Night hoss usually referred to a sure-footed horse a cowboy preferred on night watch. You won’t find the term used to describe an affliction in standard Western Americana dictionaries, like Ramon Adams’s Western Words or Win Blevins’s Dictionary of the American West.
What night hoss means in True Grit has been the subject of speculation. In the film, Cole Younger tells Mattie Ross that the Arkansas humidity was hard on Rooster Cogburn, leading to a flare up of night hoss. No further explanation is given.
I have heard that night hoss is a cowboy reference to a restless horse that keeps him awake at night, or possibly demons from alcohol that tormented a cowboy in his old age. Too bad author Charles Portis is so reclusive; otherwise he could tell us what he meant.
Marshall Trimble is Arizona’s official historian. His latest book is Wyatt Earp: Showdown at Tombstone. If you have a question, write: Ask the Marshall, P.O. Box 8008, Cave Creek, AZ 85327 or e-mail him at firstname.lastname@example.org