From quwn in the original sense of fixity; a lance (as striking fast) -- spear.
see HEBREW quwn
H7013. qayin
I. [קַ֫יִן] noun [masculine] spear ᵐ5 and most; — suffix קֵינוֺ 2 Samuel 21:16; < read קוֺבָעוֺ (compare 1 Samuel 17:38) Klo Bu HPS and others