Who invented insertion sort?

There are no records of when insertion sort was invented because people have been sorting things using the insertion sort and selection sort algorithms since before records began; they are ancient algorithms. You cannot be credited for creating an algorithm that already exists.

Shell sort, which is a refinement of insertion sort, was developed much later, in 1959 by Donald Shell. His algorithm can be credited because it takes advantage of a computer's processing abilities, whereas insertion sort and selection sort rely purely on a human's processing abilities.