“An argument; a proof.” The word occurs in the Qur’an.
Surah ii. 145: “Turn your faces towards it (the Ka’bah) that men may have no argument against you, save only those of them who are unjust.”
Surah vi 84: “These are our arguments which we gave to Abraham against his people.”
Surah vi. 150: “God’s is the perfect argument (hujjatu ‘l-balighah).
Based on Hughes, Dictionary of Islam