Like how the reciprocal of uppercase is lowercase, and of majuscule is minuscule, what is capital's own reciprocal?

Alternatively, if capital has no unique reciprocal of its own, how did it come to refer to uppercase letters without one?

Like how the antonym of uppercase is lowercase, and of majuscule is minuscule, what is capital's own antonym?

Alternatively, if capital has no unique antonym of its own, how did it come to refer to uppercase letters without one?