Contracted from qalal; light; (by implication) rapid (also adverbial) -- light, swift(-ly).
see HEBREW qalal
H7031. qal
קַל adjective light, swift, fleet; — masculine singular ׳ק Amos 2:15 +, קָ֑ל vAmos 2:14; feminine singular קַלָּה Jeremiah 2:23; plural קַלִּים Isaiah 18:2+; — בְּרַגְלָיו קַל light with his feet Amos 2:15; 2 Samuel 2:18; ׳ק, alone, swift, messengers Isaiah 18:2, pursuers Lamentations 4:19 (מִן compare), camel Jeremiah 2:23, cloud Isaiah 19:1; of swift vanishing of wicked Job 24:18 (Bu קַלּוּ for הוּא קַל); as substantive Amos 2:14; Jeremiah 46:6; Ecclesiastes 9:11, = swift (horse) Isaiah 30:16; קַל as adverb, swiftly (+ מְהֵרָה) 5:26; Joel 4:4.