chum

That made Thad think of Mark Twain, and he wondered whether the illustrious Tom Sawyer and his chum, Huckleberry Finn, had ever arranged a more fetching reception committee than this one[…]

Field had a 'chum,' or room-mate, whose visage was suggestive to the 'Sophs;' it invited experiment; it held out opportunity for their peculiar deviltry.