Fijaar means wickedness. It was named as such because the inviolability of Makkah was defiled. The arabs considered any defilement of the sanctity of Makkah to be a wicked crime.
Urwah Ar-Rahhaal ibn ‘Utbah ibn Hawaazin granted protection to No’maan ibn Al-Mundhir and his trading caravan on the way to the marketplace of Ukaadh. Al-Barraadh ibn Qais ibn Kinaanah asked, “Will you protect him against the Kinannah tribe?” to which Urwah replied, “Yes, and for that matter, I will protect him against all of mankind.”
Al-Barraadh followed the caravan hoping for an opportunity to kill No’mann. Banu Kinaanah followed to provide protection for Al-Barraadh as well as to ambush the stronger Banu Hawaazin. Hawaazin turned the tables upon discovering they were being followed. They chased Kinaanah to the edge of Makkah, fighting until nightfall. Kinaanah entered the city during the night and returned the next day with support from their allies Quraysh. Hawaazin did not enter Makkah however there enemies felt they violated the sacred space. 
Prophet Muhammad (ﷺ) said about this war, “I used to hand arrows fired by the enemies and hand them to my uncles”. It has been suggested that Allah’s Messenger (ﷺ) was twenty at the time, but collecting stray arrows for his uncles, a role young men would play in battle, indicates he was most likely fourteen or fifteen.