In its primitive sense means interdiction or prevention.
(1) In the language of the law it signifies an interdiction of action with respect to a particular person, who is either an infant, an idiot, or a slave. (Hidayah, vol. iii, p. 468.)
(2) Al-Hijr is a territory in the province of al-Hijaz, between al-Madinah and Syria, where the tribe of Samud dwelt. It is the title of the xvth Surah of the Qur’an in the 80th verse of which the word occurs: “The inhabitants of al-Hijr likewise accused the messenger of God of imposture.”
Based on Hughes, Dictionary of Islam