twain

twain \tweyn\, adjective:

two.

Here two gentlefolks whisper together, and there other twain, their swords by their side.
-- Charles Reade, The Cloister and the Hearth, 1861

Or one can say that East is East and West is West, and in American literature never the twain shall meet.
-- edited by Walter B. Rideout, Sherwood Anderson: A Collection of Critical Essays, 1974

Twain comes from the Old English twēgen, which is the masculine nomiative and accusative form of the word "two."