According to The Lancet, the concept of herd immunity originated during the early 20th century in the field of livestock veterinarian medicine, and entered the field of human medicine in the 1920s and 1930s, when doctors published data indicating that if enough children became ill with measles, the numbers of new infections would decrease until a new vulnerable population of children came along.

As you can see, the original definitions of herd immunity had nothing to do with vaccination. Rather, it described the natural course of infectious disease.