When ‘Isa ‘alayhi ‘Salam sent, the children of Iarael were required to follow and obey him. the followers of ‘Isah and his companions are called “An-Nasara”, because gave and support each other.
They are also called Ansar (helpers), as ‘Isah said:
من أنصارى الى الله قال الحواريون نحن أنصارالله
“Who will be my helpers in Allah’s cause?” Al-Hawariyyun said: We are the helpers of Allah.” (61:14)
It was said that said that they were called “Nasara”, because they inhabited a land called “an-Nasirsah (Nazareth). as Qatadah,Ibn Jurayi and Ibn ‘Abbas were reported to have said Allah knows best.
Nasira is certainly plural for Nasran.