"Gauss himself apparently coined the term with reference to the "normal equations" involved in its applications, with normal having its technical meaning of orthogonal rather than "usual"." (Wikipedia)
The interpretation of "normal" to mean "common" came later, and even then refers to the distribution itself being "the norm" rather than the distribution being about comparisons to a hypothetical "normal" object.
"Gauss himself apparently coined the term with reference to the "normal equations" involved in its applications, with normal having its technical meaning of orthogonal rather than "usual"." (Wikipedia)
The interpretation of "normal" to mean "common" came later, and even then refers to the distribution itself being "the norm" rather than the distribution being about comparisons to a hypothetical "normal" object.