Named as Gabriel Gate because the Prophet (PBUH) met with Gabriel at that spot during Bani Quraidha incursion. It was known as Uthman Gate for being located against his house.
Muhammad bin Ishaq, may God have mercy on him, said: “In the morning, the Prophet (PBUH) and the Muslims left the trench back to Medina, and dropped their weapons. At noon time, Gabriel came to the Prophet (PBUH), as Al-Zuhri told me, wearing a headdress of Istabraq (thick silk textured with gold threads), riding a mule with a saddle on its back, covered with velvet.
He said: “Did you drop the weapon, O Messenger of Allah?” “Yes.” He said. Then Gabriel said: “Angels have not dropped the weapons yet. I have now returned only at the request of the folks. Allah ordains you, O Muhammad, to take the road to Bani Quraidha.
I am heading to them to convulse them. So, the Prophet (PBUH) ordered an announcer to announce to the people: Whoever is a listener and obedient should pray Al-Asr(afternoon) only in BaniQuraidha.”
In order to know all the holy sites the foot of the Prophet (pbuh) had treaded on; download Following Prophet Footprints application which supports navigation maps without an internet connection.