"At an early stage the Yang-Baxter equation (YBE) appeared in several different guises in the literature, and sometimes its solutions have preceded the equation. One can trace basically three streams of ideas from which YBE has emerged: the , commuting in statistical mechanics, and factorizable in field theory."
January 1, 1970
https://en.wikiquote.org/wiki/Yang%E2%80%93Baxter_equation