From qadar; duskiness -- blackness.
see HEBREW qadar
H6940. qadruth
קַדְרוּת noun feminine darkness, gloom; — ק ׳שָׁמַיִם אַלְבִּישׁ Isaiah 50:3 (compare √, Jeremiah 4:28; 1 Kings 18:45; "" שַׂק).