It started to catch on early to mid eighties. There was a radical shift in the knife maker arena towards survival knives at the time. This coincided with the then new use of micarta and what is now common steels such as 154cm. Blackie Collins design of the Gerber Parabellum is considered the first custom/factory collaboration tactical folder. The term has become so overused that it has little meaning anymore. Having been in the Army from the end of Vietnam until 2000, I had a front row seat to this.