washout is a design function intended to stall the Outer portion of the wing first to allow for recovery.
I thought it's just the opposite of that. Washout makes the angle of attack of the outer portion of the wing
less than the inner. Wings stall when the angle of attack goes beyond a certain limit so with the angle less on the outer portion of the wing than the inner, the inner will stall first. This is done so the outer portion of one wing doesn't stall first causing a rapid roll to that side (tip stall). At least that is how washout is described for designing model airplanes.