Negi's staff was originally the thousand master's (Nagi Springfield) staff. 6 years ago after the demon
attack on Negi's village, the thousand master passed it onto Negi as a momento.
Since, Negi has considered the staff his "most treasured" possession. It is his signature Foci, as he always carries it around with him, usually rapped tightly with bandages. The bandages can unwrap from the staff (presumably via wind magic) allowing Negi easy usage of the staff.
After learning both magic from Eva and martial arts from Kū Fei, Negi uses his staff in conjunction with his fighting, landing blows with the staff and using the magic emitted from it, as seen in the Mahora martial arts tournament ehen Negi fought Setsuna The staff stays with him until the end of the story