ع ق لʿ-q-l
(ض) عَقَلَ يَعْقِلُ عَقْلًاʿaqala yaʿqilu ʿaqlan: to bind, to restrain; the basic sense is tying a camel with a rope (عِقَالʿiqāl = that rope).
عَقْلʿaql was given this name because it restrains a person from going astray. A Quranic point: this root occurs 49 times in the Quran and always as a verb — the noun (ism dhāt) "عَقْلʿaql" does not occur even once. Scholars have concluded from this that the Quran presents reason not as a static thing but as an ongoing activity: ﴿أَفَلَا تَعْقِلُوْنَ﴾, ﴿لَعَلَّكُمْ تَعْقِلُوْنَ﴾, ﴿لِقَوْمٍ يَّعْقِلُوْنَ﴾.