auto, register, static and extern are called storage classes in C. But why are they called classes when there are no classes in C?
The word "classes" (plural of "class") is a common English term and in this case is being used as such.
class
Pronunciation /klas/ /klæs/
NOUN
A set or category of things having some property or attribute in common and differentiated from others by kind, type, or quality.
"the accommodations were good for a hotel of this class"
"a new class of heart drug"