Nikkor was a Japanese camera brand, one of many used to avoid conflicts with the German brand Zeiss-Ikon (Can you guess which variant survives?) and manufactured the Nikkormat, a sturdy camera with nice optics used by photojournalists and hobbyists.

Addendum and Clarification: The Nikkor lenses are the remaining product of the Nikkor line. The brand 'Nikkor' was used to avoid the conflict that would be generated by using Nikon when there was already a German company named Zeiss-Ikon. While Nikkor became Nikon, there was a period where it branded everything from cameras to accessories to lenses. As Nikon was formed, Nikkor was relegated to the brand of lenses that it is today.