The term "the fringe" has its origin in the Edinburgh International Festival.
"It was not until 1948 that Robert Kemp, a Scottish journalist and playwright, described the situation: "Round the fringe of official Festival drama, there seems to be more private enterprise than before ... I am afraid some of us are not going to be at home during the evenings!". The name 'fringe' stuck and from its origins in Edinburgh it became a universal term for a certain type of artistic experience."
https://www.edinburghfestivalcity.com/the-city/history-of-th...