People will call it a notch if they don't know the purpose . It is called a lock because it locks the bearing and prevents it from spinning in the bore. A notch is cut into a surface the bearing lock is stamped in.
The notch would be in the bearing bore to accept the lock that is stamped in the bearing.
Have never heard notch reference to a bearing before. Interesting, if the picture of the bearing wasn't there, I would not have known what the op was talking about.
