An Etymological Dictionary of the German Language/Schrei
Schrei, m., ‘cry, scream,’ from MidHG. schrî, schrei, OHG. screi, m.. ‘cry, call, shout,’ allied to schreien, MidHG. schrîen, OHG. scrîan, str. vb., ‘to cry out.’ The str. verbal root skrī̆, which is without doubt genuinely Teut., is wanting in the other OTeut. dials.