TgO Ex10:22 :וַהְוָה חְשוֹך קְבַל בְכֹל ארעא דמצרים תְלָתָה יוֹמִין‏ : there was dark gloom in the whole land of Egypt for three days
See the entire entry for ḥŭšoḵ, ḥuškā n.m. darkness